230 



COMPARATIVE ANATOMY 



CHAP. 



obtain increase of surface) projects into the genital cavity in the form of numerous 

 dendriform processes, the eggs being attached by simple stalks to the stems and 

 branches. In Parasira {Tremodopiis) catenulata there is a central region containing 

 more than twenty large "egg trees " surrounded by a circle of smaller "trees." On 

 the anterior wall of the gonad in Octopus there is a single but very richly-branched 

 " egg tree " (C). In Sepia, Sepiola, and Rossia the egg-bearing surface bulges out 

 in the shape of a ridge on the anterior wall of the gonad. This ridge, in Loligo, 

 becomes a nan-ow fold, the free edge of which is produced into filaments, which carry 

 on all sides simply -stalked eggs. In the OegopsidcE {Ommastrephes, Fig. 188, D, 

 Onychoteuthis, Thysanoteuthis) the region which carries the eggs is only attached by 

 its upper and lower ends to the wall of the gonad, and forms an otherwise free spindle- 

 shaped body traversing the genital cavity, and beset all over with stalked eggs. 



In Octopus and Eledone all the eggs in a given ovary are found at the same 

 stage of maturity. 



A peculiar transformation of the follicular epithelium takes place in the ovarial 

 eggs of the Cephalopoda when nearly mature. An extraordinary increase of surface 

 occurs in the shape of numerous folds, which run longitudinally along the egg, either 

 reticulating or remaining parallel to one another, and projecting far into the yolk 



Fio. 188.— -4-D, Four diagrams of the female gonads of the Cephalopoda. A , Nautilus type. 

 B, Argonaut type. C, Octopus type. B, Ommastrephes type. 1 , Aperture of the oviduct into 

 the gonad ; 2, cavity of the gonad (a section of tlie secondary body cavity) ; 3, egg-carrier. 



of the egg which they surround. This ari-angement may be connected with the 

 nutrition of the egg. 



The male germinal layer (germinal body, or testis in the narrower sense) is a 

 variously-shaped (often globular or oviform) compact organ, which usually lies free 

 in the genital cavity, suspended to its anterior wall by a thin ligament (mesorchium) 

 in which the genital artery runs. The germinal body is everywhere covered with 

 epithelium, which is continued over the mesorchium into the epithelium of the wall 

 of the gonad (endothelium of the testicular capsule). On the surface of the germinal 

 body which is turned away from the mesorchium, there is a funnel-shaped depression 

 (Fig. 189, A) ; towards this, from all sides, the tubular testicular canals which form 

 the male germinal body converge, in order to open into it. In these testicular canals, 

 between which there is a slight framework of connective tissue, the spermatozoa are 

 produced, and are passed on to the genital cavity through the depression into which 

 all the canals open ; they reach the exterior by means of the seminal duct. The 

 testicular canals originally possess a multilaminar germinal epithelium, which yields 

 the spermatozoa, and which passes at the common aperture into the outer epithelium 

 of the germinal body, and so into the epithelium of the germinal sac. 



This description applies to the male germinal body of most Cephalopoda. In 



