﻿Dec, 1856'.] 



ELLIOTT SOCIETY. 



69 



Hydroid larvae, therefore, are thus developed by gemmation, even 

 when the stock-hydroid larva is already partially changed into a 

 medusa, and the process also takes place as early as the bi-ten- 

 taculate stage. I have even reason to believe that, in some instan- 

 ces, it is going on, that is, that the stock-hydra is found still organic- 

 ally connected with other younger larvse produced by gemmation, 

 when the larva is still further advanced in metamorphosis, but in 

 all these cases, the first appearance of the bud dates, in all proba- 

 bility, before the appearance of the medusa-disk. 



The next stage is that where the proboscis has assumed its elon- 

 gated tubular form, and two tentacula have appeared. An instance 

 in which only one such bud had been developed, is seen in fig. 21, 

 PI. 6; and another with two bi-tentaculate buds is given, fig. 24, 

 PI. 6. In the first the stock-larva was quadri-tentaculate at the 

 time of the observation, and its mouth was fully formed. That of 

 the bud, however, formed at the time of the observation. The 

 oral extremity appeared very much enlarged, loosened cells were 

 seen hanging from it at intervals of considerable regularity. Not 

 many minutes after the oral extremity had assumed the bi-labial 

 form, frequently seen in the fully developed mouth, which may be 

 seen in outline at fig. 21, and at b, in the diagram, fig-. 22. In this 

 diagram it will be seen that the digestive cavities of these two 

 hydroids were in full communication with each other, although the 

 mouths of both were developed. In fig. 24, where the probosci- 

 dian scyphons are more extended, there are still only two tentacula 

 developed on the stock larva. Here, from the position of the com- 

 pound hydroid, the mouths were not visible, and it could not be 

 determined whether they were yet open, for circulation in the pro- 

 boscidian canal is no sign whatever, "that the mouth exists, since 

 before its formation ciliary circulation of the remaining unassimi- 

 lated yolk cells, which have probably much increased by fissi par- 

 ous multiplication, is distinctly visible. I have particularly noticed 

 it at this stage, forming a kind of whirlpool in the cavity of the 

 imperforate oral -bulb of the proboscis. 



Probably not long after the formation of the mouth, we have the 

 next distinct stage of growth. The larva having gradually in- 

 creased in size up to this time, now develops two more tentacula 

 having their bases in a line at right angles to that passing through 

 the bases of the two first developed. I have seen them at their 

 first sprouting from the disk, they begin as small knobs. (See PI. 

 6, fig. 24, b.) However, they speedily attain equality with the 



