CEPHALOPODA. 



B 



(1599.) Such is the simplest form of an ear ; and if the reader will 

 compare the organ above described with that possessed by the highest 

 Articulata, as, for example, the Lobster ( 1047), the similarity of the 

 arrangement will be at once manifest. 



(1600.) All the CEPHALOPODA are dioecious ; and the structure of the 

 sexual organs both of the males and females is remarkable, inasmuch as 

 it is peculiar to the class. 



(1601.) In the females, the ovarian receptacle is lodged at the bottom 

 of the visceral sac (fig. 290, p, q), enclosed in a distinct peritoneal pouch. 

 The ovary itself is a large bag, the walls of which are tolerably thick ; 

 and, on opening it, it is found to contain a bunch of vesicular bodies, 

 attached by short vascular 



pedicles to a circumscribed Fig. 296. 



portion of its internal sur- 

 face (fig. 295, a). These 

 vesicles, the ovisacs or ca- 

 lyces, as they are called by 

 comparative anatomists, are, 

 in fact, the nidi wherein 

 the ova are secreted ; and if 

 examined shortlybefore ovi- 

 position commences, every 

 one of them is seen to con- 

 tain an ovum in a more or 

 less advanced stage of de- 

 velopment. In this condi- 

 tion the walls of the ovi- 

 sacs are thick and spongy ; 

 and their lining membrane, 

 which constitutes the vas- 

 cular surface that really 

 secretes the egg, presents a 

 beautiful reticulate appear- 

 ance. 



(1602.) If the contained 

 ova be examined when 

 nearly ripe for exclusion, 

 each is found to be com- 

 posed of a yelk or vitellus enclosed in a delicate vitelline membrane, and 

 covered externally by a thicker investment, the chorion. When the 

 ovum has attained complete maturity, the ovisac enclosing it becomes 

 gradually thinned by absorption, and ultimately bursts, allowing the 

 egg, now complete with the exception of its shell, to escape into the 

 general cavity of the ovarium (c). The oviduct (e) communicates im- 

 mediately with the interior of the ovarium by a wide orifice, the dimen- 



A. Generative organs of the female Cuttle-fish. 

 B. A bunch of eggs. 



