ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 407 



a chorion membrane, which is a secretion of the pellicular epithelium, 

 and secondly by the vitelline membrane, which is formed by a hardening 

 of a peripheral zone of the egg-cytoplasm. In Sepiola and Loligo the 

 chorion is also secreted by the follicular epithelium. Particular attention 

 is paid to the formation of the micropyle. 



y. Gastropoda. 



Natural History of Haminea solitaria Say.* — W. M. Smallwood 

 has studied this Tectibranch mollusc with especial reference to its life- 

 history. The egg-laying period extends from the middle of June to 

 the end of August, during which time the adults migrate from the deep 

 water at Wood's Hole into shallow ponds and lagoons. The eggs are 

 laid in a gelatinous mass, spherical in form, attached to eel-grass, algae, 

 stones and sticks. The eggs pass from the one-celled stage to the free- 

 swimming embryo in seven days. In its method of segmentation, 

 Haminea solitaria is in close agreement with other molluscs. No 

 positive results were obtained from attempts to produce abnormal 

 segmentation. 



Nematocysts of iEolids.f — Gr. H. Grosvenor brings forward as 

 evidence that the nematocysts of iEolids are derived from their prey, 

 the following : Not only are nematocysts of iEolids and Ccelenterates 

 identical in plan of construction and mode of discharge, but each of 

 several distinct types occurs in both groups. A single type of nema- 

 tocyst does not occur uniformly throughout a species, but different 

 individuals of the same species may have quite different nematocysts ; 

 moreover, a single individual may have nematocysts of several different 

 types, found in as many distinct species or groups of Ccelenterates. 

 When it is known on what Ccelenterate an 2Eolid has recently been 

 feeding, the nematocysts of the two are found to be identical. Also 

 the nematocysts from the faeces of an iEolid, which are generally 

 admitted to be derived from their food, are always identical with at 

 least some of the nematocysts from the cnidosacs. Those Solids 

 (Janidse, Fionidae, and Calma glaucoides) which habitually feed on 

 animals other than Ccelenterates, have no nematocysts. No plausible 

 account of the development of nematocysts in iEolids has been given, 

 though several attempts have been made. This view affords a satis- 

 factory explanation of the function of the ciliated canal through 

 which nematocysts and other indigestible bodies have been observed to 

 pass from the gastric diverticulum to the cnidosac. Strethill Wright's 

 experiments have been confirmed. In one case three Rizzolia peregrina, 

 having only small pip-shaped nematocysts in their cnidosacs, were fed 

 on Pennaria cavolinii, the nematocysts of which, after a month, had 

 almost entirely replaced the original pip-shaped ones. 



Palaeozoic Pteropoda.J — F. Chapman describes a number of fossils 

 of genera Styliola, Tentaculites, Hyolithes, etc., from Palaeozoic forma- 

 tions in Victoria. Their characters as Pteropoda are considered, the 

 author classing them in this group with a certain amount of reserve. 



* Amer. Naturalist, xxxviii. (1904) pp. 207-25 (16 figs.). 



t Proc. Roy. Soc, lxxii. (1903 ; pp. 462-86. 



X Proc. Roy. Soc. Victoria, xvi. (1904) pp. 336-42 (1 pi.). 



