316 3Jit. A. IIAKCOCK ON THE ANATOMY 



througli the loop, and, following the curvature of the intestine, 

 opens by the side of the anus into the cloaca. The vas deferens 

 terminates near to the same point, and is adherent to the oviduct 

 throughout its course. In the vicinity of the ovary it receives 

 several much attenuated branches from either side of the intes- 

 tine ; these divide dichotomously, the ultimate twigs terminating 

 in elongated and irregularly lobulated vesicles, which are spread 

 over the intestinal tube, and Avhich also exhibit a tendency to 

 dichotomous division: these vesicles secrete the male element. 



In A. scabra, A. qffinis, A. mentula, and A. venosa the same 

 arrangement of the reproductive organs is apparent ; but the 

 ovary in A. mentula is a lobulated organ, and, lying within the 

 loop of the intestine, is seen at both sides of the alimentary tube, 

 and consequently has the appearance of being double; and in 

 A. venosa, the male vesicles are exceedingly minute and are very 

 numerous. In A. parallelogramma the genitalia have much the 

 same disposition; the ovary, however, which is branched and 

 lobulated, is spread out-on both sides of the alimentary tube — as 

 is likewise the male organ, the secerning vesicles of which are 

 clustered into dendritic systems. 



These organs, however, are modified to a much greater extent 

 in the CyntMadcB — in many of which it is not easy to determine 

 the parts, on account of their intimate union ; and very careful 

 examination is requisite in these cases. In Stycla tuherosa the 

 so-called ovaries are very numerous, and are studded over the inner 

 surface of the mantle, ou both the right and left side of the body, 

 causing the lining membrane to bulge out. When folly dcA^eloped 

 they form protuberant, ovate, orange-coloured masses, each having 

 at the attenuated extremity a projecting nipple-like papilla. 

 This is the oviduct, leading out of the ovarian mass or ovigerous 

 sac ; for each mass is really a sac, in the walls of which the ova 

 are developed. And firmly attached around the base of these 

 sacs is a series of pale oval vesicles, which are sunk in the sub- 

 stance of the mantle, and which form for each sac a sort of cup 

 within which it rests. These vesicles are the male secreting 

 organs, and their ducts, extremely delicate tubes, pass upwards 

 over the surface of the sac, and go to join, on the median line, a 

 slender vas deferens, which, passing forward, terminates at the 

 extremity of the short nipple-like oviduct above described. Thus 

 it is seen that the so-called ovarian mass is a compound organ, 

 combining both the male and female parts, each with its proper 

 secreting organ and duct. There are therefore as many oviducts 



