HARGITT: PENNARIA TIARELLA AND TUBULARIA CROCEA. 173 
resulting in x- and y-shaped figures. ‘The spindle becomes radial, the 
asters are lost, though the centrosomes remain, and the first polar cell 
is formed. ‘There is some evidence that before the second maturation 
spindle forms, the chromatin remaining in the egg reorganizes: into. a 
nucleus with a definite membrane, the chromatin taking on the con- 
dition typical of the so-called resting stage. A second maturation 
spindle and a second polar cell are formed. ‘The chromosomes re- 
maining in the egg form the egg nucleus. ‘This is usually composed 
of several distinct vesicles, which may fuse at once or remain distinct 
till the time of conjugation with the sperm nucleus. 
3. Fertilzation.— When spermatozoa are present in considerable 
numbers, they may entirely surround the living egg, but nearly always 
they appear to be more plentiful at one or two places than elsewhere. 
In some of the living eggs a very definite cone on the surface of the egg 
was seen at the place where the spermatozoa were most abundant, 
and in several cases there were apparently two cones present in one 
egg, spermatozoa being collected about both of them. Whether the 
cone is a true “ céne d’attraction”’ or a “‘céne d’exsudation”’ (Fol, ’79) 
could not be determined on account of the impossibility of ascertaining 
whether it was formed before or after the entrance of the spermato- 
zoon. An entrance cavity, such as was found in coelenterates by 
Metschnikoff and by Brauer, | have never seen. After the medusae 
were liberated, the eggs sometimes retained their position on the 
manubrium. When, in such cases, spermatozoa were present in the 
water, some of them gained access to the ova, for sections of such eggs 
showed that fertilization had occurred under these circumstances. It 
is probable that the tissues surrounding the eggs had been mapas 
before the spermatozoa gained access. 
Hargitt (:00) speaks of a sort of “‘convulsive surface torsion”’ of the 
egg of Pennaria soon after the spermatozo6n enters, and I, too, found 
that under the same conditions the surface of the egg became irregular, 
and then after a short time apparently rounded out again. Sections 
show that about the time of entrance of the spermatozo6n the cyto- 
plasm ‘is extremely active; protuberances are extended from many 
points of the surface of the egg, some rounded, others elongated. 
Some of these seem to become entirely detached, whereas others are 
apparently withdrawn. Somewhat later, when conjugation of the 
germ nuclei is about to occur, the surface of the egg as a rule appears 
regular and smooth. 
As has already been stated, the polar cells arise before the eggs are 
discharged, and hence usually before the spermatozo6n enters. In a 
