CEPHALOPODA. 



635 



231 



membranous part of the oviduct, the vitellus expands, the folds dis- 

 appear, and the surface of the egg is smooth. There they acquire 

 the chorion and receive additional layers of a thick albuminous matter 

 from the gland of the oviduct, which may be compared to the shell- 

 secreting cavity in the oviduct of the fowL The ova are connected 

 together in characteristic clusters by the secretion of the superadded 

 nidamental glands when these are present. 



In the Argonaut the minute ova are appended by long filamentary 



stalks to the cavity of the involuted 

 spire of the shell where they are 

 hatched. In the Tremoctopus the 

 chaplets of eggs are bound together 

 in the form of a staflP, by a lamel- 

 lated and subgranular secretion, and 

 are so carried, according to Kolliker, 

 attached to one of the arms. The 

 ova of the Calamary are enclosed in 

 long transparent gelatinous cylindrical 

 sheaths, and offer a close analogy to 

 the spermatophora in the male. The 

 ova of the Sepioteuthis are likewise 

 enclosed in cylindrical sheaths ; but 

 these are shorter, and contain fewer 

 ova, than in the Loligo. The eggs 

 of the Cuttle-fish are of comparatively 

 large size, of an oval form, attenuated 

 at the extremities, and each enveloped 

 in a lamellated horny covering, which 

 is prolonged into a short clefl pedicle at one extremity, and attached 

 by it to some foreign body : numbers of these ova are generally found 

 clustered together, and they have commonly received the name of 

 sea-grapes (Jig. 231). 



Of the many noble contributions to Embryology, which science 

 owes to German physiologists, none surpass in importance that* 

 from which the following remarks have been abridged. 



At the beginning of the development of the egg, in Sepia offici- 

 nalis, the germ-vesicle with its nucleus is surrounded by a small 

 quantity of colourless yolk, and all the parts of the egg grow, but 

 the germ-vesicle in a less ratio than the yolk. When the germ- 

 vesicle has reached its full size the yolk increases and acquires its 

 characteristic colour. The germ- vesicle advances close to the vitel- 



Ova of Sepia officinalis. 



* CCCXCI. 



