far chemistry will enable us to understand the rationale of these changes, and account for the developement of electricity. According to the analysis of Berzelius, the atomic constitution of starch and sugar (hydrate or crystallised) is as follows: Carbon, 7 atoms in starch, 12 atoms in sugar. Oxygen, 11 23 If, then, we suppose, that 8 atoms of starch undergo decomposition during germination, it will be found that their ultimate elements will be sufficient, under a fresh arrangement, to form 4 atoms of sugar (hydrated), 1 atom of acetic acid, and leave such a residue of oxygen, hydrogen, and carbon as to require the absorption of 10 atoms of oxygen from the atmosphere to form 4 atoms of carbonic acid, and 3 atoms of water. Thus, the 8 atoms of starch become converted into 4 atoms of (hydrated) sugar, 1 atom of acetic acid, 4 atoms of carbonic acid, and 3 atoms of water. It would be little short of excessive presumption, in the present state of physiological and chemical science, to assert that the above changes are really those which always, and only, take place: I merely venture the above remarks because they are consistent with every thing we are yet acquainted with on the obscure process of germination, and serving, in the absence of a better explanation, to account for the developement of electricity during the growth of the embryo. In limiting myself to the changes peculiar to the starch during germination, I have, of course, noticed but one of the vast series of chemical changes proper to vegetable existence: still they are more than sufficient to account for the supply of electricity in the interesting experiments of M. Pouillet; for, if we take as an instance but one of the changes already alluded to, common to the infant and adult plant (viz. the formation and decomposition of carbonic acid), we shall find that the *This reasoning will be rendered more evident to the chemical student by the aid of the following formulæ : 8 atoms starch = (104 H. +56 C. + 48 0.) Then, (104 H., 56 C., 48 O.)—(92 H., 48 C., 44 O.)=(12 H., 8 C., 4 0.), which represents the composition of acetic acid (6 Í., 4 C., 1 O.)+(6 H., 4 C., 1 O.), which requires the addition of (10 O.) to be entirely converted into 4 atoms of carbonic acid and 3 atoms of water, or 4 (C. + 2 O.) + 3 (0.+ 2 H.) N. B. In the above formulæ, it will be observed that I have followed Berzelius in the composition of water, and taken the double atom of hydrogen as unity. G. B. oxygen, at the instant of its combination with carbon, sets free positive, and the latter negative, electricity, thus developing an electric current in a certain direction: but this is not all; for, whilst exposed to the influence of solar light, healthy and adult plants decompose the carbonic acid that has, by any means, accumulated in their tissues; retaining the carbon, and evolving the oxygen; giving rise to an electric current in a direction contrary to that set in motion during the formation of carbonic acid. From a consideration of these circumstances, it is fair to presume that, in healthy adult plants, electric currents are constantly occurring in different parts of their tissues; their direction being altered by the absence or presence of light, according as carbonic acid is formed or decomposed; changes which Saussure has long ago shown to depend upon the presence or absence of the solar rays. (To be continued.) ART. VI. On the Enlargement of the Eggs of some marine Molluscans during the Period of their Hatching. By JOHN EDWARD GRAY, Esq., F.R.S., President of the Botanical Society. A SHORT time ago, in a discussion on the parasitic or nonparasitic nature of the cephalopode, usually found in the argonaut shells, I stated, as a reason for believing this animal to be a parasite, that the shell which it inhabits, when just hatched (as is proved by the size of the nucleus on the apex of young specimens), must have been larger than could be expected to come from the eggs which are found on the upper part of the cavity of the shell containing the Ocythoe. In this argument I had premised that the egg of all the molluscans, like the snails and other free-air-breathing molluscans, did not enlarge their shell after being laid. Having, however, from some observations which I have been able to make on the egg of Búccinum undàtum, found that this is not the case with all the marine gasteropodes, I hasten to correct my former theory, which, curiously enough, has not been objected to by any of the persons who have differed from me in opinion, though some of them have endeavoured to depreciate the value of the observations, by attempting to prove that the real nucleus was merely a small point on the apex of what I considered as that part. The eggs of Búccinum undàtum are (like the eggs of all the zoophagous ptenobranchous gasteropodes that I know) included in coriaceous cases, which, in this species and the allied Fùsus despéctus, are oblong, and cemented toge ther into a large oblong or rounder mass, very commonly thrown on the coast, and known by the name of oyster spat, sea roses, wash walls, and several other similar designations. These cases, which do not change their form or size after they have once been deposited, have been considered as corals by Esper and others, though these authors figure the shell which is contained on the side of them. When first deposited, they are rather soft, and contain a cream-like glairy fluid; but they shortly harden, and are, at length, filled with very numerous small, yellow, roundish eggs (a hundred or more), from one seventh to one ninth of a line in diameter, which are enclosed in a transparent membranaceous skin, and, under the microscope, appear to be composed of a number of unequal-sized transparent particles, from the 300th to the 100th part of a line in diameter. In progress of time, a few of these eggs enlarge, and appear to prevent the developement of the others; so that only four or five, on an average, come to perfection in each case. When first hatched, the animals are covered with a rather irregular shell, about one line in diameter, some being rather smaller, with acute tips, and others larger and blunttopped; so that these eggs must have increased, during the time they were enclosed in the egg-cases (supposing that they only enlarged sufficiently to contain the shells alone), from seven to nine times the diameter they were when first deposited. Applying these observations to the egg of Ocýthoe, or the animal usually found in the argonaut shells, which I proved, on examination, to be about half a line in diameter (the egg of O. Cranchii being rather larger than those of the Mediterranean species), supposing them to enlarge in the same proportion as those of Búccinum undàtum, the nucleus should be about four or five lines across, which is about the average size; so that, if there were not other reasons, which I consider unanswerable, such as the form of the body, the non-adaptation or adhesion of the body to the shell, &c., the size of the nucleus would not offer any difficulty with respect to the Ocýthoe being the maker of the shell which it inhabits. ART. VII. On Generic Nomenclature. By W. E. SHUCKARD, Esq., V.P.E.S., Librarian to the Royal Society. IN a paper on generic nomenclature, published by Mr. Westwood in the last Number of this Magazine (p. 167.), being the continuation of a paper on the same subject in Vol. IX. p. 561. of the former series, he takes occasion to cavil at my reprehension of his inaccuracy in the latter paper, in the observations I made upon the genus Pemphrèdon, contained in my Essay on the Fossorial Hymenoptera. He says I take a partial view of the case, and that I charge him with inaccuracies which I omit to point out. This would be very invidious conduct, could they not be pointed out; and would imply a wish on my part to undermine, insidiously, a fair scientific reputation. Those who know me will, I feel convinced, fully acquit me of this charge; but, as the paper may be read by many who do not know me, I owe it to myself to reply, and to show that I have asserted nothing more than the truth, nothing less than the truth, and only the truth. To prove this, as my work may not be in the hands of your readers, I will just repeat what I did say. 6 In "PEMPHREDON.-This genus was established by Latreille, in his Précis,' without naming any type; but it may be presumed to have been a male of a species of the present genus Diodontus, from his description of the mandibles. his next work, the 'Histoire,' vol. xiii. p. 325., in naming the genus Pemphredon, he does not describe the mandibles, but refers to the Crabro lugubris Fab., Sphex unicolor Panz., as the best determined species of this genus.' In his 'Genera' (which ought to be considered his final view, for, in his last work, the Règne Animal' of Cuvier, vols. iv. and v., he constantly refers to it), he describes the genus Pemphredon as having spoon-shaped and quadridentate mandibles, and adduces the P. lugubris of his Histoire' as the type; and refers the P. minutus (which he there, for the first time, states to have been the original type of his genus Pemphredon in the Précis') to the genus Stigmus of Jurine, and makes it the first section of this genus. In the Nouv. Dict. d'Hist. Nat.,' t. xv. p. 151., 1817, he further confirms this, by stating that the mandibles of Pemphredon are stronger (in comparison with Stigmus), and dentate all along their inner edge.' Thus, therefore, although the original type of this genus was the Pemphredon (Diodontus) minutus F., yet, as Latreille subsequently changed his views, I necessarily follow the course he has adopted, and consider the Crabro lugubris F. as the true type of the genus Pemphredon. I have given this history of the genus in consequence of Mr. Westwood having, by a string of inaccuracies, in a recent periodical (Loudon's Mag. Nat. Hist., No. 67. vol. ix. p. 565.), introduced confusion where the course was exceedingly clear, and this is the more unfortunate, as they are produced as an example in a paper on nomenclature, where the strictest correctness was requisite, and even additionally requisite, if such a condition be possible where accuracy is always indispensable, because he there corrects what he considers the inaccuracy of Mr. Curtis, but who is certainly right." (Essay on Fossorial Hymenop., p. 193, 194.) This is what I said; and, in justification, I will proceed in the following order. 1. I will exhibit the apparent principle upon which Mr. Westwood has acted. 2. I will endeavour to discover how far my statement is a partial one. 3. I will prove Mr. Westwood's inaccuracies. And then, lastly, I will conclude; as I presume by that time the reader will be tired of me, Mr. Westwood, and the whole affair. Firstly, then, as to the apparent principle which Mr. Westwood advocates, which, as far as I can gather from the course he has taken, seems to be that "the first name applied to a genus or subgenus should be invariably retained;" and that the author himself of the genus or subgenus should not be allowed, "without good reasons,' to infringe this law. This, I admit, is an admirable maxim, and I agree that it is important that it should be universally adopted: but, as a corollary to it, I would suggest that it is equally important that it be a fixed principle; and the indispensable condition to the establishment of a genus, that the type be at the same time exhibited, which would insure justice being done to the original describer, by the necessity for retaining his generic name to the type, whatsoever might subsequently become of its congeners, upon the occurrence of new views, or the introduction of new creatures. It is trite to advert to the vast accessions that have been made to all branches of natural history since the days of Linnæus, who must certainly be considered as the first promulgator of the modern mode of treating the science scientifically; even without doing injustice to the memory of our immortal Ray. The necessary consequence of these immense additions and new discoveries is, that the genera established by Linnæus have become either such vast receptacles as to be useless, or comparatively so, to the promotion of the object for which they were designed, or inadequate to the characteristic of the creatures introduced. To meet this difficulty, Fabricius, who succeeded Linnæus in the entomological subdivision of natural history, constructed new genera; and, in doing so, he wished to supersede what he could not improve upon in principle, and he introduced new characters; but new only in |