410 MR. HANCOCK ON A SPECIES OF HYDRA, 
cured, they multiplied rapidly, as we have seen, by gemmation, 
and at this period none of the sacs containing spermatozoa were 
observed. It was not until they had ceased to propagate in this 
way, some time in September, that the male organ was developed, 
and it was always visible afterwards, though variable in size. 
All the individuals apparently produce eggs, and all are alike 
provided with the spermatic sacs; at least the ovum, in various 
stages of development, and the male organ are seen at the same 
time, in most specimens; it isnot uncommon, however, to observe 
the male organ only, the egg probably having just left the body 
of the parent, though I do not recollect having seen the egg in 
process of development in individuals unprovided with the sperm- 
vesicles. 
It is worthy of remark, that the buds sprout from the same 
part of the body in which the eggs are developed; but I have 
seen nothing to warrant the assertion, that the ova, after impreg- 
nation, “sometimes are retained, and then grow out like buds.” 
Indeed it is probable that fecundation does not take place until 
the egg bursts through the integument, and is attached to the 
parent only by a delicate pedicle. This would appear more likely 
than that impregnation should be effected through the skin of 
the animal. Whilst watching an individual, when the egg was 
about to separate from the parent, the sperm-vesicle was fre- 
quently brought, by the contractions of the body, almost in con- 
tact with the ovum; thus fecundation might very easily be 
effected, and at a moment, too, when, from analogy, it might be 
expected to take place: more observations, however, are required 
to settle this point. 
T have also observed sperm-vesicles, Pl. VIII. fig. 6, in 7. viridis; 
in this species, they are much smaller than in the specimens from 
the Northumberland lakes, and are generally two or three in 
number, near the anterior extremity of the body, but without 
symmetrical arrangement. They are irregularly conical, with the 
base wide, within which there is likewise a distinct glandular 
body, of a green colour; the moving bodies are very numerous, 
and occupy, as in the other species, the transparent apex. The 
sperm vesicles were noticed in H, viridis, after it had ceased to 
bud, some time early in October. 
