No. 2.] THE ORIGIN OF THE SEX-CELLS. 209 
It is possible to look upon the multinucleated appearance of 
the ectoderm in the region of the germinal zone as an effort to 
prepare for the formation of the gonophore. 
Both the female and male gonophores appear as outpushings 
of the ectoderm and endoderm (PI. I, Figs. 3, 8, 9). Albert 
Lang, who, under Weismann, worked upon the budding and 
formation of the gonophores of the Eudendrium racemosum, 
Eudendrium ramosum, Plumularia Echinulata, and the Hydra 
Grisea, states, that the bud and gonophore come from the 
ectoderm alone, this layer forming both the ectoderm and 
endoderm of the new organ, the old layer of endoderm of the 
hydroid over this especial portion breaking down and disap- 
pearing. Since both Weismann and he suggest that this state 
of affairs may, in all probability, be found among all the coelen- 
terates, I undertook to solve this problem for Hydractinia and 
Podocoryne. My results show that both layers take an active 
part in forming the gonophores ; there are even karyokinetic 
figures frequently seen among the endoderm cells of the young 
stages, showing quite conclusively that this layer takes a part 
in this formation. 
In Pl. I, Fig. 3, there is a breaking down of the supporting 
lamella preparatory to the formation of the “ Glockenkern”’ from 
the ectoderm. This simple relation of the layers remains un- 
changed until they have pushed out much further. A later stage 
in the development of the gonophore we find represented in 
Fig. 4, Pl. I; here the ova are found still completely embedded in 
the endoderm, while a few cells from the ectoderm, a, 6, have 
passed in between the two layers. Apparently the bell nucleus 
arises in this way from a few cells that later divide and form 
two layers. In Fig. 5, we see an adult condition of the gono- 
phore, in which the ova have pushed out of the endoderm, but 
are still resting upon it. Thus, a small portion of each ovum 
is still bounded by the endoderm, while at least three fourths 
of each ovum is surrounded by the inner layer of the bell 
nucleus. The figures which have been given by E. van Beneden 
in his work on Hydractinia, represent the bell nucleus as 
consisting of two layers, but he considers that the ova still lie 
in the endoderm, and that the rounded ends alone protrude 
