ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 415 



tissues arise from the cell elements of the old coelomic mesoderm. The 

 greatest part of these wandering mesodermal elements is formed by 

 cells of the longitudinal musculature which have separated off from 

 their contractile substance, and have at the same time undergone certain 

 alterations in the structure and size of the nucleus. The mesoderm 

 of the trunk segments arises from certain indifferent " germ-cells," 

 which give origin to various tissues and organs. The special way in 

 which the mesodermic structures of the head segments arise, the author 

 notes, is paralleled in the ccelomic mesoderm of the head vesicle of 

 Polygorclius, which according to Hatschek is an outgrowth of the part 

 of the trunk mesoderm adjacent to it. 



Digestive Apparatus in Polychseta.* — L. Brasil has made an ex- 

 haustive study of this subject, the leading results of which may be stated. 

 At the entrance to the digestive tubes in many Polychetes there are 

 claviform glandular cells, which arise by degenerative changes of the 

 superficial cells of the epithelium. In the intestine of Lagis koreni 

 there are formations analogous to those described by Eisig in the Capi- 

 tellidge under the name of " lymphatic cell diverticula." These are the 

 seat of intense and continuous renovation. The ferment cells may con- 

 tain fat. The secretion of ferments begins with nuclear expnlsions, to 

 which the nucleolus contributes. Nuclear degenerations may occur by 

 pycnosis, karyorhexis, or chromato lysis. The old cell may be totally 

 expelled (nucleus in chromatolysis), or it may atrophy (nucleus in 

 pycnosis or karyorhexis). The epithelium is the seat of a continual 

 renovation whose intensity is in relation to the secretory activity of the 

 region in question. The renovation goes on by mitosis, which gives 

 rise to elements some of which become digestive cells (trophocytes), while 

 others retain the embryonic character. These alone retain the power of 

 mitotic division, and from their subsequent divisions result trophocytes 

 and " multiplying cells " as before. The amitoses observed in the intes- 

 tine give rise to pluri-nucleate cells, whose nuclei all degenerate. The 

 mid-gut of Lagis secretes amylase, trypsine, and probably lipase. The 

 oily-looking corpuscles so often described in the middle intestine of 

 Polychcets are not a digestive secretion, but nutritive reserves — fat, 

 localised in the intestinal epithelium ; glycogen is absent. Intestinal 

 excretion does not occur in Lagis. The differentiation of specialised 

 diverticula for a single secretion (Arenicvla), for secretion and excretion 

 {Aphrodite), marks progress towards the " liver " of molluscs. 



Revision of Annelid G-enera.f — Albert Soulier continues his careful 

 revision of the genera of Annelids from the region of Cette, discussing 

 Potamilla, Sabella, Branchiomma, Myxicolla and Polydora. His results, 

 if made available to other workers on marine Annelids, will be of much 

 value. 



Minute Structure of Nerve-cells and Epithelial Cells in Earth- 

 worms. J — Santiago Eamon y Cajal describes in these elements of 

 Lumbrkus a tubuliform structure in the cytoplasm. 



* Arch. Zool. Exp., ii. (1904) pp/91-255 (5 pis). 



t Mem. Acad. Sci. Montpellier, iii. (1903) pp. 193-278 (12 figs.). 



X Bol. Soc. Espafiola Hist. Nat. iii. (1903) pp. 395-8 (2 figs.). 



