a 
’ 
> 
Zoologischer Anzeiger 
herausgegeben 
von Prof. J. Victor Carus in Leipzig. 
Zugleich 
Organ der Deutschen Zoologischen Gesellschaft. 
Verlag von Wilhelm Engelmann in Leipzig. 
XVI. Jahre. 2. October 1893. No, 430. 
Inhalt: I. Wissenschaftl. Mittheilungen. 1. MacClure, Notes on the Early Stages of Seg- 
mentation in Petromyzon marinus, L. (americanus, Le. S.). (Schluß.) 2. Mrazek, Zur Morphologie 
der Antenne der Cyclopiden. 3. Meissner, Beitrag zur Kenntnis der geographischen Verbreitung der 
Bryozoengattung Plumatella in Africa. 4. Butschinsky, Zur Embryologie der Cumaceen. 5. Ver- 
hoeff, Bemerkungen über einige nicht publicierte Diplopoden. II, Mittheil. aus Museen, Institu- 
ten etc. Vacat. III. Personal-Notizen. Necrolog. Litteratur. p. 261—276. 
I. Wissenschaftliche Mittheilungen. 
1. Notes on the Early Stages of Segmentation in Petromyzon marinus, L. 
(americanus, Le $.). 
By Charles F. W. McClure M.A., Instructor in Biology, Princeton, College, U.S.A. 
(SchluB.) 
In those ova which were developed in water at 6°C., the first 
fur did not appear till very late and had not completely surrounded 
the ovum until the 14th hour after fertilization; while the second 
furrow made its first appearance at the animal pole at right angles to 
the first, about 4 hours later. In those ova which were placed in wa- 
ter at 8°C., the furrows made their appearance slightly earlier but in 
the regular manner. 
In the case of both fertilizations it was observed that the third 
plane of cleavage was Meridional, and in no instance Equa- 
torial, while on the other hand the fourth plane was always 
Equatorial. 
At first glance it was thought that this was nothing but an ab- 
normality, but on examining great numbers of ova it was found that 
these two planes occurred with great regularity in the order 
mentioned above and that in no instance were any ova ob- 
served where the third plane appeared Equatorially or the 
fourth plane Meridionally. 
As the two sets of ova mentioned above were hatched in the dark 
and in rather cold water, much colder in fact than that of the stream 
from which they were taken, a set of experiments were made in hatch- 
ing at much higher temperatures. 
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