284 Mr, A. Hancock on a species of Hydra 
under the effect of light. The opake swelling 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. 1 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 4, d, 
shortly opens at the highest point of the swelling, and the egg, a, 
gradually makes its way through the orifice, which as gradually 
enlarges until the egg, figs. 3 b & 4:e, is completely exposed, and 
rests, as it were, within the mouth of a shallow cup, figs. 3 e, e, 
& 4g, 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, 3d & 4f: the margins at first are 
generally undulated, as in fig. 4; afterwards the ege becomes 
almost completely globular. ‘This 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, Pl. VI. fig. 6, in the course of an hour or so became 
stationary, and feel minute globules, a, a, a, which had been 
noticed sticking to it from the first, Pl. VII. fig. 3 ¢, 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. 1 d',d, are in process of development at the 
same time, gener rally Fron opposite sides, one being more advanced 
than the other. 
