28 REVIEWS. 



In Daphnia (Moina) reetirostris he saw, not without astonishment, that 

 the spermatozoa resembled the star- formed seminal bodies of the higher 

 Crustacea. In other species of Daphnia — as, for instance, in D. magna, 

 D. sima, and D. longispina — they are small, rod-like, or conical bodies. 

 It must, however, be remarked, that Daphnia reetirostris is considered 

 by Dr. Baird as belonging to a different genus, and this great difference 

 in the spermatozoa is an additional argument in favour of the separa- 

 tion. 



The testis is simple and tubular; it generally lies along the intestine, 

 in the same position as that occupied by the ovary, and opens, after 

 a short vas deferens, immediately on the upper side of the terminal 

 hooklets. 



In D. reetirostris, indeed, it seemed to terminate in the rectum, 

 which, therefore, acts as a sort of cloaca ; but this is so unlike what 

 takes place in other species, that it requires confirmation before it can be 

 received as an undoubted fact. 



Prof. Leydig considers that the recent investigations into the mor- 

 phology of the arthropods have shown that their body consists of four 

 parts — head, thorax, abdomen, and post-abdomen. This division, which 

 was proposed byErichson for the Crustacea, has not, however, been adopted 

 by our greatest authorities on the subject. Zaddach, in his admirable 

 monograph " Die Entwickelung des Phryganiden-Eies," divides the body 

 into five parts : " Vorderkopf, Kopf, Brust, Leib, und Hinterleib," 

 though it seems unnecessary to divide the head into two parts. With 

 these exceptions, however, the opinion on this point is remarkably 

 unanimous. Siebold and Stannius, (Anat. Comp., 1850) ; Milne Ed- 

 wards, (Annales d. Sci. Nat., 1851, vol. xvi.) ; Dana, in his great 

 work on Crustacea, 1852; Owen, (Lectures on Comparative Anatomy, 

 1855); and Huxley, (Memoir on Aphis, Linnean Trans., vol. xxi, 1858), 

 all divide the body of the Crustacea into three parts — head, thorax, and 

 abdomen (the two former having more or less completely coalesced into 

 a cephalothorax). Most, however, if not all, of these eminent naturalists 

 admit that the five posterior thoracic segments of Crustacea are homo- 

 logous with certain segments which in Insects form part of the abdomen. 

 To apply the word " thorax," however, in two groups so nearly allied as 

 the Insects and the Crustacea, to two different parts of the body, is 

 manifestly very confusing, and contrary to the first principles of nomen- 

 clature. The three thoracic segments of insects correspond, according 

 to Erichson, whose views are generally adopted, to the three segments 

 which in Crustacea bear the three pairs of maxillipeds ; and the five 

 segments, which carry the legs in decapods, belong in consequence to the 

 abdomen. We ought, therefore, to alter our nomenclatures as regards 

 the Crustacea, however inconvenient such a change may be; and we must 

 for this group of arthropods, if at least we wish to keep the head and 

 thorax distinct, add a fourth division — the post-abdomen — to the three 

 generally admitted. It will no doubt be better, as a matter of conve- 

 nience, to divide the insect body also, theoretically, into four parts, 

 although practically there are but three, as in decapods. 



