122 ''^- '"i<^T*^- 



Avas also a ratlier tln'ck layer of gTaniilai- substance on its wall (PI. IV, 

 fii^. (S), ^^hi(•h I l)elieve to be the secretion oi' the shell-^'lands. Tn 

 ONflincohiJi' the ootv]) presents in cross-section a very ]K'ei]linr a])- 

 ])eararice. Its cavity looks stellate, caused by the fact that the 

 cells that constitute its epithelium have assumed a laterally 

 flattened conical form and are arrariü'cd in close series in ])arallel 

 lono-itudintil lines, so that the wall is, so t«^ si)eak, furnished with 

 pilasters projecting into the cavity of the ootyp (PL XVI, fig. 4). 

 Tliat these pilasters are e(^,mposed of cells is dear from the fact that 

 here and there in cross-sections nuclei are observed near the outermost 

 end of the secti<ins of the pilasters; the comparative fewness of the 

 miclei being a<'counted for by sup])osing that the cells have been much 

 elongated parallel to the length of the ootyp. The indi\idual cells 

 are com])letely fused with each other, and no boundary line can be 

 observed ; the furrows between the pilasters, however, probably mark 

 the boundaries l)etween the longitudinal series of cells. The wall (^f 

 the ootyp is se])arated from the mesenchyma by a distinct basement 

 membrane ; but there is n(^ membrane on its inner surface (PI. X\ I. 

 fig. 4). In Tn'stODiuiii the wall of the ootyp consists of n sort of 

 syncNtium in which nuclei -n-c sp-irscly dispersed. :ind which is 

 separated fi-om the mesenchyma by a basement membrane. 41ie 

 svncvtiimi itself stains well, is ^ery finely granular, and has no 

 membr:ine on its free surface (PI. XXII, fig. 3). The nuclei seems 

 sometimes to be very regularly distributed : for instance, in Trislowmn 

 siiiiKiliini I have obserxcd in a median longitudinal section of the 

 ootv]) ibiu- nuclei arranged in ])airs in the central portion and two 

 others :ilso arranged in a ])air near the oyiduct end (PI. XXII, 

 tig. .')) ; rhey u^^re all vesicular, stained rather weakly, and contained 

 each a single, deeply staining nucleolus. Tn Cdlicntijlc and MiViot-niijle 

 the wall of the ootyj) consists of a true epithelium resting on a l)asement 



