among the species of crocodiles, from the error of some naturalists regarding the young and the adult as different species-an error arising from the short and rounded form of the face when first hatched. In process of growth, however, the muzzle elongates, and the bones increase in size for supporting the teeth. The author remarked that this well illustrated the necessity of studying all the kinds of animals in every stage of their growth. No species could be said to have been properly observed until all these circumstances had been duly examined and noted; and though the notice of a single individual, or state of an animal, was certainly of value, it could only be regarded as a sign-post, indicating the existence of an animal which required further study and examination. Dr. Gray went on to point out that great confusion had arisen among the species of Crocodiles and Alligators. The character of the "teeth fitted into notches in the margin" was one, however, which was peculiar to crocodiles, and not common to both; nor is the African crocodile found in India, as supposed. R. Garner, F.L.S.: "On Pearls: their Parasitic Origin." Mr. Garner had examined the pearls formed in the Conway and Lancashire mussel ; not the beautiful pearls of the Alasmadon, from the Upper Conway, at Llanrwst, but those of the salt-water mussel. He attributed the same origin to all pearls, viz., the deposit of eggs by a minute species of Distoma, causing their formation much in the same way as galls are formed in plants. Dr. Cobbold was not ready to accept Mr. Garner's explanation, for he had not seen the Distoma within the pearl, nor investigated the anatomy of the parasite; and knew not, therefore, whether it was a perfect Distoma or a larva. Mr. Garner replied that the pearls of Alasmadon are not diseased ova, for it has its ova in the foot and gills, where the pearls do not occur; nor are they produced in the renal organs. They might be produced by grains of sand, &c., but then such foreign bodies could not get access to the mantle, as it is attached all round to the shell; and on splitting a pearl no grain of sand is found, but a little dark-coloured animal matter, which he considered to be the remains of the Distoma, its exuviæ, &c. In the Lancashire mussels, the Distoma was always to be found as a little yellow speck (to the naked eye) enclosed in a condensed cellular envelope, and sometimes might be found in a calcifying state. He did not think he was called upon to follow out the anatomy of the parasite. Professor Rolleston, F.R.S.: "Diastase in the Saliva, and its Action upon Starch and Inuline." Inuline, a kind of starch found in the dahlia, artichoke, &c., differs from true starch in not being changed into sugar by the converting agency of the diastase contained in the saliva, unless, indeed, it contains sugar at first. Moreover, the saliva of infants contains so small an amount of diastase, that even common starch is inconvertible by it, and therefore innutritious. Important practical results follow from this; first, that artichokes cannot be used as a substitute for potatoes, since they contain inuline instead of starch; and second, starch foods are useless in the early months of infancy, since the salivary diastase at such a period is inactive. SCIENCE SCHOOLS AND CLASSES. In the List of Science Teachers contained in our last Number we mentioned the name of Mr. H. P. Meaden, Haslingden, near Manchester, as having passed nine students with first-class Queen's prizes.-It should have been ten. We have to add that before the last examination there were 158 Science Teachers in Great Britain, and four Lecturers holding honorary diplomas. Their names will be found at the end of the last Directory published for the Science and Art Department, South Kensington Museum. We mention this, as we know of persons who have been desirous of obtaining instruction in elementary science, and were quite unaware that there was an able teacher resident in their immediate vicinity. REVIEWS. AT T the commencement of his volume, Mr. Jeffreys refers to the expensive character of the "British Mollusca," by Professor E. Forbes and Mr. Hanley, as a reason for his having undertaken the present work. No such apology was needed : naturalists who know anything of the enthusiasm of the author for his subject, and of the zeal with which, for many years, he has devoted himself to his favourite study, would have had cause for much regret if the materials thus collected had been withheld from the public, or were only to be found scattered in the many communications made by him to various scientific societies. To afford some idea of the research undertaken in preparation for the present work, we may refer to the author's account of his investigations relating to a single genus of small fresh-water bivalves :- "My own cabinet contains no less than 274 parcels of Pisidia, which have been in the course of the last thirty or forty years collected from different localities and sources, and comprise many thousands of specimens. I have personally examined the types of those species which have been described by Dr. Turton, Mr. Jenyns, Mr. Alder, Dr. Bandon, and other conchologists who have published on the subject. I have collected these tiny shells in many parts of Holland, Germany, France, Switzerland, and Italy, for the sake of comparison with British forms; and I have had to refer to numerous works in many languages in order to collate the descriptions of forty-one different species which have been proposed by European writers within the last century. Of these I cannot conscientiously recognize more than six as distinct." Although the volume now published is confined to land and fresh-water shells, the Introduction, extending to 114 pages, is quite general, and affords space for the description, in a very readable form, of most of the questions interesting to conchologists. Without expressing a decided opinion on the "origin of species," Mr. Jeffreys suggests a practical method of distinguishing between species and varieties. He says: "I believe it may now be considered a well-established rule that all distinct groups of individuals, living together, and having a common feeding-ground, and which are not connected or blended with each other by insensible gradations, are prima facie entitled to the rank of species." * British Conchology. Part I.-Land and Fresh-water Shells. By JOHN GWYN JEFFREYS, F.R.S., &c. Van Voorst. 1862. Selected on this principle, the author recognizes 121 species of British land and fresh-water molluscs; the number given in the "British Mollusca" being 125. This slight reduction in the number of species accredited to our native land is, however, far more than compensated for by the acknowledgment of no less than 187 distinct varieties, all of which are named and described; whilst, of a large proportion, the localities and other circumstances of interest are recorded. The name of a new species had, until recently, something almost magical in its attractions. Collectors were deemed fortunate who could secure the prize; its absence from a cabinet was regarded as leaving an unsightly gap; whilst varieties, however curious or distinct, were counted as little more than superfluous luxuries. Thanks mainly to Mr. Darwin, this disparity is at an end, and collectors are now in a position better to appreciate the value of labours such as those of the author, and of the large increase he has made in the number of recognized objects of attention on the part of those who desire to study the land and freshwater shells of our country. In the more difficult genera Mr. Jeffreys has, we think, succeeded in presenting the species in bolder and better relief than any previous writer. For example, the genus Zonites; the descriptions of Z. nitidus, Z. alliarius, Z. purus, Z. nitidulus, Z. radiatulus, ought to leave collectors in no difficulty in identifying these snails, even without the assistance of plates. In nomenclature the author seems to us in a few instances to have needlessly increased the difficulty of the subject by the adoption of unfamiliar names, having only a questionable claim to priority; and by alterations in orthography induced by his desire to render all the generic names significant. A mere name is at all times a most fallacious guide to the determination of a species, and young collectors, to whom alone the caution need be addressed, should in no instance affix a name on account of its supposed agreement with a specimen under examination. It is far more honourable, and in every way better for scientific purposes, to attach the place, date, and, if possible, the circumstances of its capture, and to wait patiently till it can be satisfactorily identified. In the work before us, for Balea of Dr. Gray, the more recent Balia of Swainson is adopted, as nearer "badius," a somewhat barbarous Latin word for "brown," which is, after all, a wholly unimportant indication. If the supposed meaning of a name is to give a clue to its orthography, we can well imagine the erudition which may hereafter be called into exercise by future conchologists pondering upon such titles as those of Dr. Gray's genera "Lottia" and " Pollia," the investigators being, after all, certain to hit upon no meaning half so pleasant as the fair originals. 66 In one instance Mr. Jeffreys has for a well-established name, “Pupa Anglica" of Ferussac, substituted one of his own, Pupa ringens” Jeffreys, on the plea of having been the first to describe the species, though previously figured under the familiar name; and this whilst, on his own showing, the name Pupa ringens had been used by M. Michaud for another species of the same genus. All possible consideration will, however, doubtless be extended to the author when it is understood that the vindication of his own discoveries presents itself to him in the aspect of a "parental duty" (p. 267). In many respects the present work appears to us to be far in advance of any previous one upon the subject. Together with clear, concise, and sufficient descriptions of the characters which serve to distinguish the species, are combined so many interesting observations on the habits of the animals, that the work possesses the rare merit of combining scientific accuracy with a large amount of popular instruction. We can only give one or two brief illustrations. It is well known that certain univalves, when suddenly dislodged from floating weeds, spin a thread by which, like the spider, they are able to regain their resting-places. Mr. Jeffreys records a similar habit in Sphærium lacustre (Cyclas caliculata), which also uses its foot in ascending the sides of an aquarium, and even in creeping along, suspended from the surface of the water, just in the manner common to many gasteropods. Bivalves, with the exception, perhaps, of some species of oyster, are supposed to be purely aquatic in their habits ; yet the author records, on the authority of Nilson, that Pisidium pusillum is in Sweden frequently found living between the bark and the wood of fallen trees in moist places. Helix pulchella, a minute snail common in Britain, is reported to occur in Siberia, Italy, Corsica, Madeira, North America, Cashmir, and Thibet. Some of our little wood-snails, H. aculeata and H. fusca, appear, on the Continent, to adopt habits not generally known in this country: they ascend in spring the trunks of trees, live during the summer amongst the higher branches, and in the autumn save themselves a long and laborious descending journey, by dropping with the falling leaves to their place of winter retreat. The snail has not generally found much favour in the eyes of poets; yet the author avails himself of the assistance of a friend to devote some pages to the aesthetic aspect of his subject, with especial view, as he asserts, to the gratification of his fair readers. Homer, Goethe, and "Shakspere," are cited. From the "Venus and Adonis" of the last-named a fine simile is given : "Or as the snail whose tender horns being hit, We anticipate with pleasure the volumes on the "Marine Mollusca of Britain," by the same author, and conclude this brief notice with a word of commendation for artist and publisher. Mr. Sowerby's plates, more especially the beautiful coloured frontispiece, deserve special notice; and of Mr. Van Voorst we can only repeat what has been said a hundred times before, that what ink and paper can do to render useful reading pleasant, he has done. |