410 REPORT—1863. 
ment within the gonophore, the remains of the plasma may still throw off 
portions which become developed in a similar way into free actiniform 
embryos*. 
Our knowledge of the freshwater Hydre is still in a very imperfect state, 
not only as regards the development of the embryo, but as to the structure of 
the parts on which the sexual functions devolve in these animals. Towards 
the end of autumn, and occasionally earlier, conical tubercles may be seen 
budding from the body of the various species of Hydre, and containing, when 
mature, active caudate corpuscles. There is no difficulty in recognizing in 
these corpuscles spermatozoa, and in the containing tubercles true male 
gonophores,—a determination which we originally owe to Ehrenbergt. A 
minute aperture ultimately shows itself in the summit of the gonophore, and 
through this the spermatozoa escape. 
But, besides the spermatogenous tubercles, there also occur, usually on the 
same individuals, others which, instead of containing spermatozoa, have their 
cavity occupied by a spherical body, first accurately described by Ehrenberg#, 
and which, notwithstanding some anomalous features, we are justified in 
viewing as an ovum rather than anything else; while we must regard its 
containing sac as a female gonophore—a gonophore, however, in a very low 
stage of development, for the spadix is at an early period pushed back by the 
large single ovum, and remains undeveloped, while no ectotheca appears to 
be differentiated. In the male gonophore, on the contrary, the spadix is not 
suppressed, but may be seen projecting from the body of the hydra into the 
cavity of the gonophore. The ovum, when mature, escapes by the rupture 
of the walls of the gonophore, and is then seen to be invested by a tough 
membranous shell, which in some cases has been observed to develope peculiar 
forked spines over its entire surface. In this body, however, neither ger- 
minal vesicle nor spot has hitherto been detected; and, in the development 
from it of the embryo, the polypoid form appears to be directly attained, 
without the occurrence of a planula-stage§. The structure of the ovum and 
the developmental phenomena in Hydra would thus seem to come nearer to 
what we meet with in Tubularia than to the conditions presented by any 
other hydroid. 
It will be thus seen that the earliest free stage of the Hyproip tro- 
phosome is locomotive, and shows itself under two distinct types—one pre- 
* Claparéde (Beobacht. iiber Anat. u. Entwickl. wirbelloser Thiere an der Kiiste von 
Normandie, 1863, p. 2) takes a somewhat different view of the development of Tubularia 
from that given above. His observations were made on certain minute organisms which 
he found swimming in the open sea, and which are undoubtedly the actinula-stage of some 
species of Tubularia. He compares them to small meduse, the body of the actinula repre- 
senting the umbrella, and the long tentacles the marginal tentacles of the medusa, while 
that portion which is subsequently to become developed into the stem of the Tubularia is 
viewed by Claparéde as corresponding to the manubrium,—the mouth of the future Tudu- 
laria, with its circle of short tentacles, being developed on the summit of the umbrella. Cla- 
paréde believes that he had found an aperture in the extremity of that portion which is to 
become the stem, and he has apparently thus been led to interpret this part as the manu- 
brium of amedusa. Ihave little doubt that Claparéde has been here deceived by the pecu- 
liar structure described above, and which might easily lead to an error of interpretation. 
+ Ehrenberg, Mittheilungen aus den Verhandl. der Gesellsch. naturf. Freunde in 
Berlin, 1838, p. 14. 
+ Ehrenberg, Abhandl. der Berl. Akademie, 1836, p. 115, taf. ii. : 
§ Pallas, Karakteristik der Thierpflanzen, p. 53. Laurent, Froriep’s Neue Notizen, 
No. 513, p. 101; and ‘ Nouveaux Recherches sur les Hydres d’eau douce, Voyage de la 
Bonite,’ 1844. See also ‘“‘ On the Generative System of Hydra,” by Prof. Allen Thomson, 
loc. cit., and Hancock, ‘‘ Notes on a Species of Hydra found in the Northumberland Lakes,” 
in the ‘Annals of Natural History,’ vol. v. 1850. 
