4 Prof. Allman on the Hydroida. 



fibres (muscular?) visible beneath the ectoderm of Clava, Co- 

 ryne, &c. 



Still finer strise may also be occasionally witnessed running 

 in a circular direction round the stem ; but I have not been able 

 to determine whether these represent fibres or mere rugse in the 

 ectoderm. 



Peculiar processes are given off from the stem towards its 

 posterior end. They are in the form of short blunt cones, and 

 are arranged in longitudinal series, which follow the course of 

 the canals, the stem immediately over each canal bearing two 

 alternating rows. They are tubular, with the cavity apparently 

 communicating with the canal, and with the free extremity im- 

 perforate. They appear to be extensile, for they may occasion- 

 ally be here and there seen much elongated, and then with their 

 extremities slightly clavate. In the form now described they 

 are confined to a region of the stem at some distance from its 

 lower end. They do not seem to be here employed as organs of 

 adhesion ; and I am unable to throw any further light upon their 

 nature. When, however, a specimen of Corymorpha, after being- 

 captured, has the lower end of its stem free from sand, and is 

 then transferred to a jar of sea- water, it soon begins to fix itself 

 to the bottom of the vessel, and at the end of about twenty-four 

 hours its base is seen to be surrounded by a delicate web, which 

 closely adheres to the vessel, and in a few days has spread itself 

 over a surface of a square inch or more in extent. Under the 

 microscope this web is found to be composed of a multitude of 

 fine tubular filaments, which are given off from the stem all 

 round, close to its lower end ; and after repeatedly crossing one 

 another so as to form an entangled web-like tissue, they termi- 

 nate each in a slightly expanded or clavate and imperforate ex- 

 tremity. The filaments are composed of a granular substance, 

 which, as it continues to elongate, invests itself with an exceed- 

 ingly delicate structureless tube or polypary. In these filaments 

 of adhesion it is impossible not to recognize structures essentially 

 similar to the conical tubular processes given off from the stem 

 a little higher up. 



The entire stem is invested by a very delicate, colourless, and 

 transparent polypary. For the greater part of the length of the 

 stem the polypary lies close to it, and may be easily overlooked; 

 but further down it becomes separated by a considerable interval, 

 and here constitutes a loose corrugated sac, in which the lower 

 end of the stem is enveloped. 



Gonophores. — The gonophores are borne on the extremities of 

 the branched tubular stalks already mentioned, where they are 

 grouped in compact clusters consisting of buds in every stage of 

 development, from the minute tubercle in which no medusoid 



