1 86 DESCRIPTIONS OF PREPARATIONS. 



contort! of the Mammalian kidney. Guanin and uric acid have been stated to 

 occur in the gland. Grobben compares the terminal lobe with its rich vascular supply 

 to the Malpighian capsule ; the remaining sections to the tubuli uriniferi of the 

 Vertebrate kidney. The shell gland of the Phyllopoda and Copepoda consists of a 

 similar terminal lobe and tube, but it opens on or close to the second maxilla. 



The ovary is a trilobed gland like the testis, but the fissures between the lobes 

 are not so deep. The oviducts originate as do the vasa deferentia, but they are 

 wide, short, and straight. The ovary is lined by a delicate cuticle. The ovum is 

 developed by the growth of a single cell out of a small mass of cells. It has a 

 vitelline membrane, and when ripe, is set free into the cavity of the ovary. It is 

 fecundated externally to the body, and is suspended to the feet, sterna, &c., of the 

 abdomen during the development of the embryo. For the mode of suspension and 

 the cement glands, see ante, p. 166. 



The testis is a tubular gland. The tubes branch, and the ultimate branches 

 end in a number of short stalked vesicles varying in size according to the state of 

 their contents. The lining cells multiply and are differentiated into spermatozoa. 

 These bodies are disc-like structures with a number of slender curved rays attached 

 to the circumference of the disc. The structure of the disc is still somewhat 

 obscure. The spermatic fluid is milky, and contains a viscid substance which 

 agglutinates the spermatozoa into thread-like spermatophores. The sperm is shed 

 through the channels of the first pair of abdominal limbs. The second pair are 

 worked to and fro in these channels as if to keep them clear. The male throws the 

 female on her back and deposits the sperm on the ventral surface of the last pair of 

 swimmerets and on the thoracic sterna round the oviducal apertures, parts which are 

 approximated during oviposition. 



Branchiae. Huxley, P. Z. S. 1878; Glaus, Arb. Zool. Inst. Wien, vi. 1885. 



Digestive tract-, structure of walls, glands, and epithelium, Vitzou, A. Z. Expt. 

 x. 1882; Braun, Arb. Zool. Zoot. Inst. Wurzburg, ii. 1875, iii. 1876-7; Frenzel, 

 A. M. A. xxv. 1885. Ossicles of stomach and muscles. Mocquard, A. Sc. N. (6) xvi. 

 1883; T. J. Parker, Journal Anat. Phys. 1877; Albert, Z. W. Z. xxxix. 1883. 

 Working model of gastric mill. Roth, Nature, xxi. 1879-80. Pyloric filter. Huxley, 

 The Crayfish, p. 58. Gastrolith. Braun, Arb. Zool. Zoot. Inst. Wurzburg, ii. 1875 ; 

 Chantran, C. R. Ixxviii. and Ixxix. 1874; its chemical composition, Bulk, Miiller's 

 Archiv (Arch. f. Anat. und Phys.), 1835. 



Structure of liver. Frenzel, Mitth. Zool. Stat. Naples, v. 1884. Its Chemical 

 action. Krukenberg, Untersuch. Phys. Inst. Heidelberg, ii. 1882. Its Colouring 

 matter. MacMunn, P. R. S. xxxv. 1883. 



Green gland. Wassiliew, Z. A. i. 1878; Grobben, Arb. Zool. Inst. Wien, iii. 

 1881. For guanin and uric acid in it, cf. Griffiths, P. R. S. xxxviii. 1885. 



Testis. Lemoine, A. Sc. N. (5) x. 1868; Rougemont, Organes ge*nitaux, &c., 

 Astacus, Bull. Soc. Sc. Nat. Neuchatel, ii. 1880 (not seen). Spermatozoa. Grobben, 

 Arb. Zool. Inst. Wien, i. 1878; cf. note in Huxley, The Crayfish, p. 354. Spermato- 

 genesis. Sabatier, C. R. c. 1885 ; Hermann, C. R. xcvii. 1883. 



Fecundation. Chantran, C. R. Ixxi. 1870; Ixxiv. 1872. 



Structure of ovum. Waldeyer, Eierstock und Ei, Leipzig, 1870, p. 85; cf. general 

 account by Ludwig, Arb. Zool. Zoot. Inst. Wurzburg, i. 1874. 



Cement glands. Braun, Arb. Zool. Zoot. Inst. Wurzburg, ii. 1875 ; iii. 1876-7. 

 Their secretion and fixation of ova. Lereboullet, A. Sc. N. (4), xiv. 1860. 



