546 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



nearly central position.* This band of tissue has been 

 called by Ishikawat the " germogen," to contrast it with 

 the " vitellogen " — the rest of the ovary where the yolk 

 elements are found. It is transparent in the fresh 

 condition and is readily distinguishable from the purple 

 eggs; in preserved material it is even more distinct, 

 showing up white amidst the red ova. The ova in the 

 ovary are enclosed in a follicular epithelium. The cells 

 which are about to form the follicles are almost 

 indistinguishable from the very young ova. The mature 

 eggs are crowded together closely, and partly lose their 

 rounded form by mutual pressure. The protoplasm of 

 the ovarian egg has a characteristic radially striated 

 appearance, and there is a membrane enclosing the egg — 

 the primary egg membrane — which arises apparently 

 from the peripheral protoplasm. A second membrane of 

 a tougher nature, which is probably secreted by the cells 

 of the oviduct, is present on the ripe egg. The walls of 

 the oviduct before oviposition are very glandular. 

 P. Mayer correctly states that there is but a single 

 nucleolus in all the stages of the ovarian egg, and he also 

 says that the freshly laid egg is not furnished with a 

 nucleus and is a cytode. It is well known, however, that 

 the chromatin of the germinal vesicle is often lost during 

 maturation, and it is this phenomenon probably that 

 accounts for the condition to which he refers. 



The " Cement " Glands on the under-surface of the 

 abdomen are accessories to the reproductive organs 

 proper. They all consist of the type of gland we have 

 noticed before — that is to say, a globular structure of 

 pyramidal cells from the central cavity of which an 



* Cf. Bumpus, American Lobster. Journ. Morph. V., p. 215, 

 1891. 



t Quart. Journ. M.S. XXV., p. 391, 1885.. 



