348 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
are kept on a stove heated to about 30° C., the great majority show in 
about 18 hours the exogastrula state. The rudiment of the archenteron 
is turned outwards. There is, however, no such increase of the growing 
zone as Herbst describes. 
Some 24 hours after exogastrulation, the larva assumes the familiar 
prismatic form, calcareous needles appear, the gut is divided into three 
parts, but these are not expanded. On the contrary they shrivel and an 
“ Anenteria ” larva, preceded by an “ A nentoblastia ” stage, results. 
The second chapter is entitled “ Variations in the formation of 
Micromeres, or the result of diluting the sea- water.” Various degrees 
of dilution induce numerous variations in the formation of micromeres, 
and yet normal Plutei often resulted. 
A third set of experiments concern the relations of ectoderm and 
endoderm. The micromeres were removed, cells of the “ animal ” and 
“ vegetative ” half remained, and a normal Pluteus was formed. From 
cells of the “ vegetative” half alone (4-8) a normal gastrula developed, 
and likewise from cells of the “ animal ” half alone. Driescli therefore 
concludes that the micromeres are not essential, and that the formation 
of the two layers does not imply previous qualitative differences in the 
blastomeres. 
Thus, according to Driesch, the cells of the segmented ovum are 
equivalent, and organogenesis is induced by differences of position and 
by external stimulus, acting on the self-differentiating plasma. 
Dr. T. H. Morgan * has made experiments on Arbacia punctulata, 
Asterias Forbesi , and on crossing Arbacia and Asterias, the one an 
Echinoid, the other an Asteroid. With regard to normal cleavage the 
author made the interesting observation that as early as the two-cell 
stage the protoplasm of the Arbacia-e gg is not isotropic, as the micro- 
mere area is already foreshadowed. The details of various experiments 
are given, but their interest is shadowed by the author’s conviction that 
he has succeeded in fertilizing the eggs of Asterias with the sperm of 
Arbacia. 
Deep-Sea Echinoderms of Eastern Mediterranean.! — Dr. E. v. 
Marenzeller reports that twenty-six species have been collected. As in 
other cases it is found that species supposed to be more or less littoral 
extend to considerable depths ; thus Astropecten pentacantlius was taken 
at 629. metres, Palmipes membranaceus from 400-600 metres, Spatangus 
purpureas at 620, and Synapta digitata at 629 metres. Some of the 
dredged species were known only from the Atlantic, like Echinus nor- 
wegicus or Holothuria intestinalis. Others are described for the first time, 
and of these Gnathaster \_Odontaster\ mediterraneus and Kolga ludwigi 
are perhaps the most interesting. The high temperature of the water of 
the Mediterranean appears to be the cause of the general absence of deep- 
sea Holothurians, most of which are inhabitants of cold water. At 
certain points the extreme outposts of the littoral forms mix with the 
species proper to deep waters. The author expresses the belief that 
improved methods of dredging will reveal the presence of at present un- 
discovered species. 
* Anat. Anzeig., ix. (1893) pp. 141-52 (4 figs.), 
f Denkschr. K. Akad. Wiss. Wien, lx. (1893) pp. 1-24 (4 pis.). 
