204 Miscellaneous. 
bell-nucleus forms a flattened conical mass; but in most other 
specimens that have come under my observation it is more elon- 
gated at this stage. The migration of the germ-nuclei have already 
begun. These are characterized by having their chromatic substance 
concentrated in a comparatively small number of large pieces, one of 
which usually occupies the centre of the nucleus and is larger than 
the rest, while the others are in most cases situated close to the 
nuclear membrane. The germ-nuclei are, as a rule, considerably 
larger than those of the ordinary entodermal cells and are spherical 
in form. In the accompanying diagram four germ-nuclei have 
already passed into the bell-nucleus, and a fifth is just passing the 
supporting layer. 
Now the point to which I wish to call special attention is the 
formation of the bell-nucleus by the wandering in of interstitial cells 
from the ectoderm. This fact I believe to have satisfactorily proved, 
at least to myself, by a comparison of a large number of sections. 
I have never seen any of the definitive ectoderm-cells undergoing 
mitosis; but, on the contrary, the interstitial cells can be observed 
in all stages of migration to form the bell-nucleus. In the section 
from which the accompanying diagram has been drawn a stream of 
protoplasm could be observed around many of the migrating nuclei ; 
and in most of the sections numerous interstitial cells with amceboid 
processes are everywhere present in the ectoderm of the gonophoral 
bud. This indicates that they are in active migration. I believe 
also that some of the interstitial cells divide in the gonophore, for 
in some sections I have observed spherical nuclei with a vesicular 
appearance and with a small number of large chromatin pieces. 
This I take to be an indication that they are undergoing recon- 
struction from a recent mitosis. Two such nuclei are drawn in the 
diagram at the entrance of the bell-nucleus. 
The youngest stage of the so-called female gonophore that I have 
been able to obtain was far more advanced than the male gono- 
phore represented in the diagram. The cavity of the bell-nucleus 
has been formed and is lined by a distinct epithelium of columnar 
cells. But exactly the same process that takes place in the male 
gonophore can be observed to occur with even greater distinctness. 
The interstitial cells of the ectoderm crowd in towards the entrance 
of the bell-nucleus, and are there seen to arrange themselves one by 
one into a distinct epithelium, and form a part of the lining of the 
cavity of the bell-nucleus. In the so-called female gonophore the 
cells that have wandered in and formed a part of the epithelium 
afterwards undergo repeated division, while in the male gonophore 
no such has been observed. 
It seems to me that Physalia presents in this respect an inter- 
mediate stage between those forms in which the bell-nucleus is 
formed as a solid niass of cells from the ectoderm and such form as 
Coryne pusilla, in which, according to Weismann, cells migrate 
singly into the endoderm and there form the bell-nucleus afterwards. 
—Johns Hopkins University Circulars, vol. xiv. no. 119, p. 80. 
