604 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Ians. These, however, may turn out to be larval, for their respective 
discoverers, Greeff and Schaudinn, did not observe any sexual repro- 
duction, whereas Murbach found gonophores on Hypolytus. 
It is a single unbranched polyp of the Tubularian type, with two 
circles of tentacles, ten in the upper and fourteen in the lower. A primi- 
tive perisarc envelopes the hydrocaulus, at the free end of which buds are 
given off by spontaneous fission. These in turn develope directly into 
polyps like the parent. Ova and spermatozoa are developed in gono- 
phores situated just above the aboral circle of tentacles. The polyp 
moves slowly from place to place. 
Mr. Murbach also describes Corynitis agassizii McCrady and its 
medusoid, which is identical with Gemmaria gemmosa McCrady. He 
notes, inter alia , that the polyps of the European and American Gemmaria 
are generically distinct, and yet the medusoids are almost identical. 
Development of Aurelia aurita.* — Herr Walter Hein gives a brief 
summary of his results on this subject. The blastula consists of a 
hollow cone of similar cells with a ventral blastocoel. Certain cells 
wander out of the blastoderm and undergo degeneration in the blasto- 
coel, but delamination does not occur. Endoderm arises by a typical 
invagination, but the cells show considerable variations in form and 
size, which are probably due to differences in nutrition. Later these 
differences disappear. The blastopoVe does not close entirely, but 
persists as a narrow canal which, after the fixation of the larva, widens 
out into the permanent mouth. During gastrulation isolated cells of 
the endoderm may go free, and then finally degenerate in the cavity of 
the archenteron. These degenerating cells are quite distinct from those 
of the blastula stage, fragments of which may be found between the 
two embryonic layers. When the gastrula elongates to form the planula, 
the endoderm of the oral pole can be distinguished from that at the 
aboral by the smaller size of its constituent cells. This proliferation 
of oral endoderm increases with the fixation of the larva, but no trace 
of ectodermal gullet or gut-pockets was observed. The four primary 
tentacles originate simultaneously. Gastric ridges and grooves originate 
from the endoderm, and four ectodermal invaginations of the peristome 
form the muscles. 
Abnormalities in Aurelia.f — Herr E. Ballowitz has followed other 
zoologists in making a study of the variations of Aurelia aurita , which 
seems a good subject for the modern statistical method to tackle. This 
jelly-fish seems to be extraordinarily variable ; but perhaps this impres- 
sion should be corrected by the fact that we know more about it than 
about many others. The variations are both peripheral and central. A 
whole paramere may be absent, or one may be added, or more than one. 
Sexpartite, pentapartite, and most rarely tripartite individuals occur. 
A tripartite Aurelia has a three-cornered mouth, three genital pouches, 
six marginal bodies, &c., but often the variation is not so uniform 
throughout. Some of the abnormalities may date from the Ephyra- 
stage, but most must have a much earlier origin. 
* Zool. Anzeig., xxii. (1899) pp. 353-4. 
f Arch. Entwickmech., viii. (1899; pp. 239-53 (1 pi.). See Zool. Centralbl., vi. 
(1899) pp. 626-8. 
