284 Mr. A. Hancock on a species of Hydra 



under the effect of light. The opake swelKng extends nearly 

 round the body, — the margins being generally distinct. This is 

 the nascent ovum, as it appears at first ; it gradually increases 

 in size, PL VII. fig. I d', and ultimately becomes very protu- 

 berant, bulging the body excessively on one side : the egg at this 

 time is confounded with its covering; but it, d, is soon seen as 

 a rounded, somewhat flattened body contained within a trans- 

 parent envelope, e, resembling the general surface of the body, 

 of which it is apparently a continuation. This envelope, fig. 2 b, b, 

 shortly opens at the highest point of the swelling, and the egg, a, 

 gradually makes its way through the orifice, w^hich as gradually 

 enlarges until the e^^, figs. 3 Z* & 4 e, is completely exposed, and 

 rests, as it w^ere, within the mouth of a shallow cup, figs. 3 e, e, 

 &> 4<ff, the contracted envelope. The egg remains in this position 

 for a day or sometimes longer, attached to the body of the parent 

 by a short, thin pedicle, figs. 3 c? & 4/: the margins at first are 

 generally undulated, as in fig. 4 ; afterwards the egg becomes 

 almost completely globular. It is ultimately detached, and soon 

 fixes itself to some foreign body. On watching one individual 

 through the microscope, the egg was observed to separate from 

 the parent, and to move slowly away. No ciliary action could 

 be detected to account for the motion ; but it assuredly passed 

 out of the field of view as often as the instrument was adjusted : 

 in another instance, however, no motion could be observed. The 

 egg, PI. VI. fig. 6, in the course of an hour or so became 

 stationary, and several minute globules, a, a, a, which had been 

 noticed sticking to it from the first, PL VII. fig. 3 c, c, enlarged, 

 and others made their appearance : they soon assumed the cha- 

 racter of delicate cells, fig. 7, filled with globular bodies with 

 dark margins. These globules are probably composed of some 

 tenacious mucus with which to glue the egg to any substance on 

 which it may happen to settle. Soon after attachment these 

 bodies disappear, and the egg, which is now perfectly circular, is 

 seen to be surrounded by a narrow, transparent rim, indicating 

 the presence of a distinct chorion ; the under side of the egg being 

 flattened, the upper side convex, opake and rosy as at first. 



I have not been able to determine with precision how many 

 eggs are produced by each polype, but certainly no great number, 

 probably not more than three or four, and in some instances 

 perhaps only one. On one occasion after the egg separated from 

 the animal, the latter gradually dwindled in size and ultimately 

 disappeared. Most frequently, however, the polype is not 

 materially altered on giving birth to an egg; and occasionally 

 two, PL VII. fig. I d', d, are in process of development at the 

 same time, generally from opposite sides, one being more advanced 

 than the other. 



