1906] YAMANOUCHI—POLYSIPHONIA VIOLACEA 417 
the auxiliary cells are formed. The membrane of the female nucleus 
appears to dissolve at its point of contact with the sperm nucleus, 
which lies closely pressed against it (fig. 14a), and later the chromatin 
content of the male nucleus enters the female (fig. 115a). The 
subsequent changes in the female nucleus result in the gradual trans- 
formation of its linin network into clearly defined chromatin granules 
and finally into chromosomes. At the same time the crowded group 
of male chromosomes (fig. 115a) becomes looser, the chromosomes 
separating from one another, some remaining near the periphery of 
the fusion nucleus, and some passing into the interior. Finally the 
chromosomes derived from male and female nuclei become mingled 
together and the fusion nucleus assumes the appearance of prophase 
(fig. 116). 
The first mitosis of the fusion nucleus (sporophytic).—The fusion 
nucleus which results from the union of the male and female gamete 
nuclei now passes into the prophase of mitosis. The number of chro- 
Mosomes is 40, which is of course double the number in the 
sexual plants or gametophytes, so that the fusion nucleus is sporo- 
phytic in character. These chromosomes differ from one another 
in size, and some of the smaller certainly come from the male nucleus. 
It would be interesting to trace carefully the history and behavior of 
these chromosomes, but I am not prepared at present to discuss this 
Matter in detail. 
The stages of prophase in Polysiphonia, as previously described, 
are always characterized by the presence of centrosphere-like structures 
i the poles; however, these structures do not seem to be present dur- 
ing the first mitosis of the fusion nucleus. The spindle of this mitosis 
'S remarkable for its size and the breadth of the poles (jig. 1174). 
Another peculiarity is the fact that the nuclear membrane disappears 
during prophase, so that the spindle lies freely in the cytoplasm. It is 
Possible that the early dissolution of the membrane is connected 
With the fusion of the gamete nuclei, which may weaken the mem- 
brane of the female nucleus. As regards the count of chromosomes, 
their number 40 is apparent when the equatorial plate is viewed 
ftom the pole (fig. 118a). In the late metaphase the same number 
may be estimated in both groups of daughter chromosomes (jig. 123), 
Which means that this first division of the fusion nucleus is a typical 
