excited by this most singular and beautiful phenomenon, than presently the body of the animal, which had been quite transparent, and bearing much resemblance, in aspect, to some of the marine Rhizóstomæ, becomes dotted with a number of distinctly circumscribed circular spots, of a dark blue colour, exactly corresponding to that of the moving particles of indigo. In some species, particularly those which are provided with an annular contraction or neck (such as the Rótifer vulgaris), separating the head from the body, the particles of indigo can be traced in a continuous line in their progress from the mouth to these internal cavities. Dr. Ehrenberg used a microscope possessing a power of 800, made by Chevalier of Paris; but a power of from 300 to 400 he found sufficient in most cases. For the purposes of measurement he used a glass micrometer, constructed by Dollond, which gives directly the ten thousandth part of an inch, and permits of a much smaller quantity being correctly estimated, as it contains the astonishing number of 400 equal parts distinctly cut in glass within the space of half a line. By means of a micrometer screw, which has since been constructed by Pistor of Berlin, he has been enabled to measure one fortyeight thousandth of an inch, or one four thousandth of a line; a degree of minuteness which is never necessary in actual practice.

By the above infusory mode of rendering the animalcules obvious, and by such a microscope and micrometer to explore their structure and functions, Ehrenberg has demonstrated the existence of a digestive system in all Müller's genera of the Infusòria. The cilia, which vary in number in different species, seem to be the principal agents by which they excite those currents which are so beautiful under the microscope, and which have the effect of bringing the nutritive particles infused into the water into contact with their mouths. The mouth merits the notice of the systematologist; from the very precise characters which he can draw from thence for his subordinate divisions. An oesophagus belongs only to those animalcules which possess a notable contraction between the mouth and the stomach. Of the last-named organ (stomach) some species have several; the Mònas térmo has four, and other species more; the stomach varies in form also, in different species. The alimentary canal presents, as in other classes of the animal kingdom, the utmost variety, in respect to form, situation, and degree of complication: the anus, also, in its figure and situation, exhibits much variety.

In the muscular system of these beings, Ehrenberg has

distinguished eight muscles by name, and disclosed numerous additional facts of great value.

In their generative system, he has proved the existence of all three modes of generation; the viviparous, the oviparous, and the gemmiparous. Some species of the animals are hermaphrodite. Besides clearly demonstrating these three systems (the digestive, the muscular, and the generative,) to exist in these minute beings, Ehrenberg conceives that he also discovers in them a vascular and a nervous system: but the two latter are not considered as yet clearly demonstrated.

Professor Ehrenberg, in his travels in Siberia, found several new genera and species of infusory animalcules, which have already been alluded to in our Vol. IV. p. 255.

In consequence of these most remarkable and important discoveries in the anatomy of these animated atoms, a totally new classification of them has been elicited. Previously, the apparently homogeneous tissues of these minute beings furnished no distinctive characters except the varieties of external form, the presence or absence of cilia and other appendages; which are so uncertain, and so changeable, that they have been long ago rejected from other departments of zoology as the fundamental bases of division. Dr. Ehrenberg now forms a classification of them according to their organisation. To follow him through his classes, orders, families, sections, and genera, would lead us too far. For the examination of these, we refer the reader to the January number of the journal quoted; venturing to remark that the scheme of classification there exhibited (p. 82-86.) seems characterised by the deepest and most patient investigation, by clearness of contradistinction, and by ability of expression. Dr. Gairdner remarks that Ehrenberg has "included under his categories those genera or species only, whose digestive organs he has demonstrated himself by his new method of observation." A plate (pl. iv.) exhibits magnified figures and dissections of Monas térmo and átomus Müller, Leucophrys pátula Ehr., and Hydátina sénta Ehr.; and displays the wonders of their intestinal structure and general organisation.

The geographical distribution of these beings, invisible to our unaided sight, is the next and last part of the subject discussed. It occupies twelve pages, and is replete with interest. Dr. Ehrenberg has prosecuted his researches on this subject (as well as on others) in extensive journeys in Africa and Arabia, and in Russia, Siberia, and the Altaï mountains; and he has discovered species in the subterranean waters of the silver mines of these mountains, at the depth of 56 fathoms.

MISCELLANEOUS INTELLIGENCE.

ART. I. Retrospective Criticism.

CORRECTIONS to the last two Numbers. In p. 128, last line, for " Ambleside," read "Keswick." P. [206.], line 8. from the bottom, for "Nemains," read "remains." The work entitled " Popular Lectures on the Vertebrated Animals of the British Islands" is wrongly arranged, p. 76., among the natural history works of North America.

Stoat. (p. 77.) — J. M. remarks, "the stoat does not change its colour [in winter] here, as in the northern parts." This remark reminded me of a very fine specimen of the stoat in its white state, caught near this place in January, 1830; and which was much finer than many specimens brought from abroad, being all over of a beautiful snowy white colour, forming a striking contrast with the black tip to its tail. This was the first perfectly white British specimen I had ever seen; but I have seen many partially white. I am, Sir, yours, &c.-E. H. Greenhow. North Shields, Jan. 28.

1832.

Crows covering their Eggs on leaving the Nest. (p. 144.) The crows in the vicinity of Lee uniformly cover their eggs, after they have begun to hatch, with the materials of the lining of the nest; and if they comport themselves differently at Walton Hall Park, I should infer the latter to be eccentric crows. I speak positively to the fact as to our crows in Kent; and I doubt not some hundreds of testimonies may be got to prove the fact. -James Rennie. Lee, Kent, March 2. 1831.

Couch's Fishes of Cornwall new to the British Fauna. (p. 15.) — Sir, In this article, I have serious fault to find with the disregard of proportion exhibited in two of your figures. The wrass (Labrus lúscus L.), p. 18., is described as being 22 in. long by 24 in. deep; your figure (fig. 5.) represents its depth as at least equal to one third of its length, and so 7 in. deep instead of 21 in. In p. 21., the dusky perch is described as 3 ft. in length and 7 in. in depth; the figure (fig. 7.) represents it as 12 in. deep. I am, Sir, yours, &c.-G. A. Goswell Road, Feb. 6. 1832.

G. A. is thanked for his useful and judicious corrections. That he offers on the Scomber maculatus, spotted or Spanish mackarel (fig. 8. p. 22.), arises from his own misapprehension of the term " compass." It is described as 6 in. in compass; that is, in circumference, and not in depth, as G. A. has understood it. — J. D.

The Opinions of the Reviewer of Newman's Essay on Sphínæ vespifórmis (p. 187.).-Sir, Without prejudice to the merits or novelty of Mr. Newman's ingenious arrangement of insects, reviewed in p. 187., which I have not it present leisure to investigate, allow me to point out how completely the magical circles employed in the construction of his diagrams appear, from their symmetry, to have blinded the reviewer, so far as the binary division of insects into the subclasses of Mandibulata and Haustellàta is concerned; and to show how slightly Mr. Newman's general arrangement really differs from that adopted in my Systematic Catalogue with reference to such subdivision.

My arrangement, divested of the symbolic circles, stands thus:

In this last arrangement, if we place the genus Thrips in its proper location, at No. VII., and the A'ptera of my Catalogue at No. V., their situations between the typical mandibulated and haustellated groups clearly point out, according to the general fact that the characters of any conterminous group assimilate with those of the adjoining, their tendency to become mandibulate; while, on the other hand, if the Trichoptera be placed at No. 5., the cause of their being mandibulate, or approaching thereto, is equally manifest. It is, therefore, evident, that, by considering insects as divisible into two great groups, in accordance with Clairville's views, his followers are not guilty of such "glaring inconsistencies" as a mere prima facie appearance indicates; and I may add that his arrangement was not " unhesitatingly adopted” by me. It may also be observed, that the location of the A'ptera in my arrangement corresponds with the tendency of opposite points of the circle to resemble each other, as discovered by MacLeay. I am, Sir, yours, &c.-J. F. Stephens. March 2. 1832.

Stýgia not a New Holland Genus, as stated in Mr. Newman's Essay on Sphinx vespifórmis. Sir, In my friend Newman's excellent little essay, Stygia is said to be a New Holland genus: I feel myself bound, in justice to my friend, to state that this error arose from my inadvertence, and his too great confidence in my accuracy. One species of this genus is a native of France, and one, I believe, of North America; but none have been found in New Holland. Allow me to request from your readers an attentive perusal of this ingenious work, and a careful comparison of the system therein propounded and the quinarian, the only other system which can be said to be an approximation to nature. I am, Sir, yours, &c. - E. Doubleday. March 12. 1832.

British White Butterflies. Sir, In Mr. Rennie's excellent paper on this interesting subject (Vol. II. p. 224.), no mention is made of Hipparchia Galathea, which surely as legitimately deserves a place among the white butterflies " as Gonépteryx rhámni; and this is admitted. I am, Sir, yours, &c.-C. Nov. 25. 1831.

A figure of the Hipparchia Galathea will be found in p. 338. of our present Number (fig. 74. b); and also one of a most remarkable variety of the same species, in p. 335.; with valuable remarks on each, in their respective places, by Mr. Bree. The valuable strictures of this gentleman, in Vol. III. p. 242., on the probability that Póntia Chariclèa is merely a

* Like all systematists whose schemes are shackled by numbers, Mr. Newman finds it convenient to omit such orders as Strepsíptera, &c. (printed above in Italics), as they militate against the harmony of the cabalistic seven; though they are palpably of greater importance than any septenary division of either of his larger circles.

+ The position of Oikéticus amongst the Lepidoptera, while Psyche is distantly removed into the Neuroptera, is unquestionably inconsistent with a natural arrangement; yet those genera are so placed by Mr. Newman: thus showing, when detail is attempted, how futile all our systems become.

variety of Póntia brássica, and P. Mètra but a variety of P. ràpæ, should ever be read collaterally with Mr. Rennie's article (Vol. II. p. 224.), which excited them. No figure of P. Napæ æ occurs in that article (Vol. II. p. 227.), which Mr. Bree regrets (Vol. III. p. 245.). — J. D.

Insect Monstrosities. — In recording (Vol. IV. p. 476.) the case of an E'later murinus found with one of its antennæ three-branched, the fact of a Chlànius vestitus having been found with a supernumerary appendage to the fourth joint of one of its tarsi, as figured and described in Vol. II. p. 302., is cited as a somewhat parallel instance. Two still more remarkable cases of insect monstrosity, as mentioned by Mr. Dale (Vol. IV. p. 21.), should have been added to this citation.-J. D.

London Fogs. (p. 304.) — To J. M.'s useful remarks on this subject, it may be well to register the following supplementary ones: they are transcribed from an ably written, and very recently published, pamphlet, entitled," Dr. Weatherhead's Account of the Beulah Saline Spa, at Norwood, Surrey." The site of the Beulah Saline Spa is the village of Norwood, seven miles south of London, which stands on one of those elevations known as the Norwood Hills. Dr. Weatherhead remarks: "From trigonometrical observation, it has been computed that the height of these hills is about 390 ft. above the level of the sea at low water. By accurate observation of the height of the fog, relatively with the higher edifices whose elevation is known, it has been ascertained that the fogs of London never rise more than from 200 to 240 ft. above the same level." [The level of the sea, not that of Norwood, as appears by the second sentence following.] "In some instances, the line of demarcation between the pure air and the fog is distinctly defined; on other occasions, the latter dissipates itself so gradually into the superincumbent atmosphere as to show no line of separation. Thus placed above the fogs of the plain, and removed from the smoky and contaminated atmosphere of the metropolis, the air [of Norwood, and the neighbourhood of the Beulah Saline Spa, is meant] has long been celebrated for its pure and invigorating qualities." — J. D.

Anchor Frosts. - Since reading the articles by J. M., p. 91., and T. G., p. 303., on this phenomenon, I have met with the following, which I beg to hand to you:-"It is a curious particular in the natural history of the Thames, that it always freezes just at the bottom: this habit is often found to prevail among rivers in Germany, particularly in the northern parts; but is asserted by the writer of the article Ice, in the Encyclopædia Britannica, never to be met with in the more temperate of the European climates. The fact is assuredly otherwise: the congelation of the river Thames uniformly commences in the lowest places. The mass then formed rises, on a rude calculation, to about the middle of the water, where it presents, as on the streams of Germany, a resemblance to the partial consolidation of nuclei or small hail. A second mass then forms at the bottom; the central mass rises to the surface, and the new bottom, or ground ice, takes its place, and gradually mounts to the superior fabric, with which it speedily assimilates. Dr. Plott accounts for this circumstance, by supposing that the water of the Thames is more abundantly impregnated with salt than that of other English rivers; and that, as salt naturally sinks to the bottom, and as naturally inclines to a state of congelation, the formation of ice consequently takes place first at the greatest depth." (Faulkner's Chelsea, p. 19, 20.)

Anchor Frosts. (p. 91.) On the subject of anchor frosts, it is merely a long and severe one, wherein large masses of ice are frozen to the stones and gravel at the bottom of rapid streams; not, as your intelligent correspondent J. M. states, by crystals of ice floating down the streams, and accumulating amongst the stones; but simply by the stones acquiring a degree of cold far below the freezing point, and the water in contact with them