368 
of cleavage is not an Equatorial one, but consists like that of 
the Ctenophorae of two Meridional furrows. 
Such a variance from the accustomed mode of cleavage must 
need considerable corroboration before it can be accepted and I can 
not say positively that it is constant for all seasons. But that it was 
so this spring there can be no doubt as the following facts show. 
Between May 20th and June 1st of this year, thirty specimens of 
P. marinus were obtained from a stream in the neighbourhood of Prin- 
ceton. Of these, at first two different females were stripped of their 
eggs which were fertilized artificially in the usual manner with sperm 
taken from two separate males. That is, the eggs were sqeezed out of 
each female into clean shallow porcelain dishes, and after a few se- 
conds the sperm from a ripe male added, together with a small amount 
of fresh water. The contents of the dish were then carefully stirred 
about a few times with a lampreys tail, so as to be sure that the sperm 
would come in contact with all of the ova. At the end of thirty minu- 
tes all of the water was poured off and fresh added. This process was 
continued until all traces of the sperm had disappeared from the wa- 
ter. Finally the ova were placed in hatching jars through which a 
continuous stream of fresh water passed and the jars kept in a fairly 
dark cellar. The temperature of the water at the time of the first fer- 
tilization was 6°C. while that of the second which took place one 
week later was 8°C. 
Concerning the first and second planes of cleavage nothing re- 
markable was observed as in every instance, so far as noted, they were 
Meridional and at right angles to each other conforming in every 
respect to the generally accepted views on this subject. It may also 
be added that with very few exceptions, every ovum was fertilized and 
passed through the early cleavage stages. 
(Schluß folgt.) 
II. Mittheilungen aus Museen, Instituten etc. 
1. Die zoologische Station in Rovigno. 
Von Dr. Hermes, Berlin. 
eingeg. 22. Juli 1893. 
Die inneren Einrichtungen der vom Berliner Aquarium erbau- 
ten zoologischen Station in Rovigno sind so weit vorgeschritten, daß 
sechs Gelehrte in derselben arbeiten können. Zwei Arbeitstische 
stehen zur Verfügung des deutschen Reiches, zwei werden vom preußi- 
schen Cultusministerium vergeben und über die letzten zwei Tische 
hat sich das Berliner Aquarium die Disposition vorbehalten. Indem 
