ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 169 



but that they disappear during early embryonic life. " The re-appear- 

 ance of these toxic substances in the organism is correlated with the 

 development of the poison-glands. The poisons formed by these glands 

 pass into the blood after the manner of internal secretions, and at the 

 time when the ovary becomes active, they become associated with the 

 germ-cells to contribute to the formation and the development of 

 the egg." 



Toxic substances are known in the eggs of certain fishes and sea- 

 urchins, and Phisalix thinks that they probably have an important role 

 in oogenesis and development. " Perhaps they form a material basis 

 of inheritance, and serve to transmit the chemical characteristics of the 

 species," — which seems a large conclusion to draw from the premises. 



Development of Tarsius Spectrum.* — A. A. W. Hubrecht notes 

 that the placentation of this aberrant type is pronouncedly " deciduate," 

 while the arrangement of the foetal membranes, with the diminutive 

 yolk-sac, rudimentary allantois, and large extra-embryonic ccelomic 

 space, brings Tarsius near the monkeys and man. 



The author describes the maturation, fertilisation, segmentation, etc., 

 and pays particular attention to the germinal layers. The material for 

 the extra-embryonic coelom springs from the posterior end of the blasto- 

 derm ; in continuity with it is formed the primitive streak in the centre 

 of which is the rudimentary blastopore or neurenteric canal. The 

 mesoderm is formed from an anterior tract of hypoblast (as frequently 

 in Amniota), and from a peripheral ring (as described by the author in 

 the shrew). 



To solve the problem of the germ-layers, Hubrecht goes back as far 

 as a Coelenterate type, and asks us to see in its gastrovascular cavity 

 and stomodamm the fore-runners of the blastopore and notochord 

 respectively. 



Development of Lens.f — Em. Mencl discusses the difficult case of 

 the development of a lens apart from any direct contact between the 

 brain and the epidermis. 



Notes on Development of Lizard. — Karl Peter finds that while 

 the primitive plate is essentially an ectodermic proliferation, some endo- 

 dermic cells are included along with it. He re-affirms his conclusion 

 that there are in lizards five pairs of gill-clefts, and that the supraperi- 

 cardial body is the homologue of a pair of gill-clefts. 



b. Histology. 



Secretory Phenomena in Poison-Glands and Digestive Glands.§ — 

 L. Launoy has made a detailed study of the poison-glands in the viper, 

 newt, scorpion, centipede, etc., and of the digestive glands in crab and 

 hermit-crab. In the active glands, whether poisonous or digestive, the 

 nucleus of an actively secreting cell is the seat of " passive phenomena " 



* Furchung und Keirablattbiklung bei Tarsius spectrum. Amsterdam, 1902, 

 115 pj.. and plates. See Nature, lxvii. (1903) pp. 341-2. 

 t Auat. Anzeig., xxiv. (1903) pp. 169-73 (15 rigs). 

 t Tom. cit.. pp. 156-G4 (4 figs.). 

 § Ann. Sci. Nat. (Zool.), xviii. (1903) pp. 1-224 (2 pie.). 



April 20th, 1904 n 



