ARGONAUTA ARGO AND THE HECTOCOTYLT. J5 



In one of the specimens without any externally visible penis 

 there projected from the cleft in the back a transparent, pointed, 

 ovate vesicle of a few lines in length, which contained merely 

 a fluid, and at its fixed end was drawn but into a more delicate 

 fine tube of about the same length. The latter appeared 

 when the vesicle, in consequence of being frequently touched, 

 detached itself, and was evidently formed analogous to the 

 ductus deferens ; it consisted of a longitudinally striated cord 

 (i.e. perhaps a folded tube) and an external, distant, structureless, 

 partially laminated sheath. The larger vesicle therefore may per- 

 haps be considered as an earlier form of development of the bulb, 

 with which the vas deferens generally begins. Other changes in 

 the latter and in the penis appear to belong to a later period. In 

 two Hectocotyli which were met with in copulation upon female 

 Tremoctopoda {vide infra), the abdominal capsule was also open 

 and empty, probably in consequence of long lying in water. 

 The penis, however, with the external part of the ductus deferens 

 plainly visible in it, was distinguished on both occasions by a length 

 of an inch and a half. It passed out of the skin, not in the middle 

 line, but nearer to the right-hand series of suckers, and close 

 to the penultimate pair, which plainly arose from its being torn. 

 Its outermost third appeared to be similar to the whole free part 

 of the penis in other cases ; the two upper thirds were thinner, 

 as if pulled out longitudinally. After the skin was taken away 

 from the place of exit of the penis as far as the abdominal cap- 

 sule, the portion of the penis lying below it was seen to pass 

 below the axis obliquely towards the last sucker of the left side, 

 and there cease. This inner part of the penis formed a fusi- 

 form enlargement, which appeared to be hollow. The outer- 

 most layers of the penis passed into the surrounding fibrous 

 tissue, but the connexion with the axis was no longer recogni- 

 zable. In all probability these changes of form of the penis and 

 ductus deferens are connected with the function of copulation, 

 and a third Hectocotylus, in which the outermost portion of the 

 penis was plainly torn off, but the inner end had the same rela- 

 tion as in the other two, had probably already performed this 

 act. Its abdominal capsule also was open and empty. The 

 eversion of the ductus deferens for the purpose of ejaculation, 

 indicated by Von Siebold (/. c. p. 411), appears to take place. 



