of Mollusks in Holothurise. 25 



there were no molluskigerous individuals ; generally, however, 

 there was one, two or three, and sometimes even four such. 

 These were neither larger (or older) nor smaller (or younger) 

 than the others — young and old were found of each kind. 



The individuals with normal ovaria never possessed the un- 

 branched molluskigerous organ, and those possessing the latter 

 organ were never provided with the ordinary branched ovarium 

 of Synapta. 



The molluskigerous individuals may be very easily distin- 

 guished externally from the others, the semitransparency of the 

 body permitting us readily to see whether it contain the common 

 ovarium or the thick molluskigerous organ. 



On the spontaneous fission of these animals, it of course readily 

 happens, that the generative organs, which open externally at the 

 head end, become torn, and are found partly in the separated 

 head-portions, partly in the headless fragments. In the same 

 manner the molhiskigerous organ is found, either torn from its 

 connexions, and lying loosely coiled up in the abdominal cavity ; 

 or still attached to, and in organic connexion with, the Syn- 

 apta, I have so frequently observed this organic connexion 

 (twenty times), that it is beyond doubt, and must be supposed 

 to exist in all cases. The connexion is a double one — by both 

 ends ; the ordinary ovaria are attached only to the head, where 

 they open, while in the opposite direction they float perfectly 

 free in the abdominal cavity ; but the molluskigerous organ when 

 uninjured is attached not only to the head where it opens exter- 

 nally, but by its lower end to the intestine in the manner to be 

 described immediately. There may be from one to three mol- 

 luskigerous sacs in the same individual. 



The structure of this molluskigerous one nowise resembles 

 that of the ordinary generative organs. The tube is uninter- 

 ruptedly continuous throughout, but is differently coloured in its 

 two halves. The portion attached to the intestine is always 

 green, the other is coloured yellow by its contained yelks. So 

 far as the sac is green, it contains an intus-suscepted portion of 

 itself, with a blind end, like the inverted finger of a glove ; and 

 at the point of intus-susception it is connected with the intestine, 

 or rather with the intestinal blood-vessel, which gives off a branch 

 to invest the open end of the intus-susception. The mode of 

 this connexion is very extraordinary. Where the sac is embraced 

 by the vessel it is enlarged into a sort of knob, from the middle 

 of which the involuted portion passes into the interior of the sac. 

 The open mouth of the cavity of this portion therefore projects 

 into the cavity of the blood-vessel, and the blood not merely^ 

 bathes the knob, behind which walls of the vessel are attached to 



