ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
799 
phora and Callianira it has no special relation to the meridian bands, 
there is in Beroe just under the basal cushions a layer of longitudinal 
and a layer of transverse fibres, which cause the contractility of the 
ctenophoral plates. 
With regard to the difficult question of the systematic position of 
the Ctenophora the author urges that even if they can be shown not to 
be derived from polyp-like forms the similarity of the gastrovascular 
system offers a great difficulty to separating them from the Cnidaria, 
and he concludes with urging various considerations in favour of the 
hypothesis that the Turbellaria are derived from the Ctenophora. 
Segmentation of Ovum of iEquorea Forskalea.* * * § — Dr. Y. Hacker 
finds the ovum of this large Craspedote a suitable object for the study 
of the early stages of the egg of the Medusae. The first stages are gone 
through with the greatest regularity ; the nuclear divisions as far, at 
least, as the 64-stage are, under normal circumstances, quite simul- 
taneous, and the blastomeres appear to be normally all of the same size. 
Where there are irregularities there are pathological forms of nuclear 
divisions, and the cell-complex loses its spherical form. Before the 
directive corpuscles begin to be formed the ovarian nucleus takes on 
a vesicular form ; the sperm-nucleus always has a radiate form. With 
regard to the law as to the number of chromosomes the author thinks it 
is clear that all known cases may be arranged in one of these systems, 
and that closely allied forms are generally seen to belong to one and the 
same system. 
Growth of Clavularia ochracea.f — Herr G. v. Koch observed that 
the longitudinal growth of a stolon of this coral continued during a 
period of twenty days at an almost constant rate of slightly over • 5 mm. 
per diem. On an average a new polype was formed every six days. 
Heteromorphosis of Hydroids.J — Herr Hs. Driesch describes the 
diverse modes of growth in two forms of Sertularella , which, though 
nearly related (if indeed different) species, behave quite differently in 
relation to external influences. As the one is affected by light, so is 
the other by the force of gravity. His results, and those of Loeb, with 
a discussion of which the j> resen t communication is in great part 
occupied, “ are all against the interpretation of development as a 
specialization of an essential substance (idioplasm). A segmentation- 
cell may according to its position take part in one or another organ of 
a Sea-urchin, and a polyp may give rise to another polyp or to a stolon, 
and a stolon to another stolon or a shoot, according to the influencing 
conditions.” 
Hydrocorallinge of Torres Straits. § — Dr. S. J. Hickson has a notice 
of a small collection of Hydrocorallines, represented by Millepora 
Murray i, Distichopora violacea , and Stylaster gracilis , made by Prof. 
A. C. Haddon in Torres Straits in 1888-9. The author thinks it, 
probable that in some cases the male, female, and immature colonies 
of one and the same species have been made separate species, and 
* Arch. f. Mikr. Anat., xl. (1892) pp. 243-63 (2 pis.). 
f Morphol. Jahrb., xviii. (1892) pp. 605-8 (1 fig.). 
X Biol. Centralbl., xii. (1892) pp. 545-56 (3 figs.). 
§ Scient. Proc. Roy. Dublin Soc., vii. (1892) pp. 496-510 (3 pis.). 
