REPRODUCTION OF ALCYONIDIUM. 63 



canal becomes distinguishable, so that the young animal soon exhibits 

 an exact representative of the original from which it sprung. 



(134.) But here it is necessary to observe that this kind of vege- 

 tation does not take place indiscriminately from any portion of the 

 tegumentary surface of the polyp. The reproductive gemmae are only 

 formed immediately over the track of one of the eight longitudinal 

 membranous lamellae above noticed (fig. 27, 1), so that the apertures of 

 communication between the newly formed polyps and the original are 

 always so placed as to interrupt the course of one of these folds. 



(135.) It is not, however, only by the development of buds that the 

 reproduction of the Alcyonidium is effected. These animals likewise 

 produce ovules or gemmules adapted to spread to a distance their 

 sedentary race ; and it is worthy of remark that the same organs from 

 which the gemmas above described derive their origin, perform the 

 functions of the ovaria of higher animals. 



(136.) It is in the longitudinal membranous folds above described 

 that the reproductive gemmules are developed (fig. 27, 2), which, as 

 they increase in size, become pedunculated, and ultimately fall off into 

 the abdominal cavity, whence they easily escape through the mouth of 

 the polyp. 



(137.) The intestiniform convoluted organs (fig. 26, 1, &), situated 

 beneath the alimentary cavity, are, from what has been stated above, 

 evidently not the ovaria, seeing that the ova are formed elsewhere ; 

 neither, from the simplicity of the structure of the reproductive ap- 

 paratus, can they be regarded as male organs destined to fertilize the 

 ova ; so that, upon the whole, it seems most probable that they repre- 

 sent hepatic vessels. 



(138.) When the polyps are expanded, their mouths are frequently 

 seen to dilate and take in the surrounding water, which, together with 

 such alimentary substances as may be suspended in it, penetrates into 

 the digestive canal, and through this passes into the general cavity of 

 the abdomen, whence again it mounts up into the tentacula through 

 the eight canals that surround the alimentary tube. It results from 

 this arrangement, that the thin and variously folded membrane com- 

 posing the bodies of these animals is bathed throughout with the 

 water required for respiration, and that all its internal surface is 

 placed in contact with the nutritive matters more or less elaborated 

 in the stomach. 



(139.) On seeing the same animal producing sometimes buds or 

 gemmae, and sometimes ova, Milne-Edwards was led to inquire into 

 the cause of this difference, which he believes to be of a mechanical 

 nature. In those parts of the polyp which are not yet imprisoned in 

 the growing mass of the polypary, reproduction is generally effected by 

 the development of external buds, while towards the base of the 

 polypary, where the constituent zoophytes are intimately united to- 



