104 THE AQUARIAN NATURALIST. 



the polyp, and each cyst hangs by a pedicle from this 

 stalk (PI. II. fig. I,/). The integument of the cyst is 

 rather of a fleshy consistence, either opake, or so thin 

 and transparent as to expose its contents; each contains 

 a solitary embryo, which, on arriving at maturity, is 

 expelled slowly and gradually as a minute white solid 

 substance, from a dilateable orifice at the extremity. 



Soon after expulsion an irregular zone or waving 

 line may be recognized on the circumference of the 

 embryo, which within a day denotes originating ten- 

 tacula. In earlier stages the animal resembles a star 

 with obtuse rays, or the spokes of a wheel. The 

 centre is next prolonged in opposite directions, on the 

 one side as extending tentacula, on the other as the 

 neck or stalk of the Hydra. Meanwhile the circum- 

 ferential tentacula exhibit enlarged extremities, by 

 means of which the nascent animal, sustaining itself in 

 a position the reverse of that which it will ultimately 

 assume, can voluntarily change its place. The central 

 portion forming the stomach next augments in size, 

 the swelling extremities of the tentacula refine into 

 points ; the animal, still a simple Hydra endowed with 

 locomotive faculties, next reverses its position and 

 becomes permanently rooted on the plane supporting 

 it, assuming the appearance and characteristics of a 

 Tubularia (PL II. fig. \ 9 g). 



Such is the issue of this remarkable process, and 

 that sometimes within twenty-four hours after the 

 expulsion of the embryo from the ovarian cyst. The 

 clustering ovaria are generally confined to the largest 

 heads, and for the most part March and April may be 

 held to be the chief season of propagation, though, as 



