SEX DETERMINATION IN DINOPHILUS GYROCILIATUS. 353 
This appearance is quite irregular, however, and is simply 
the result of the rapid drawing apart of the two masses of 
chromatic substance. These bodies, in the case of the female 
chromatic substance, are figured in figs. 49, 51, 53, 54, 61, 
and 64. The same appearance is presented also by the male 
substance during division, but on account of its much smaller 
volume is not so distinct. The female substance is always 
crowded with peculiar yellowish refractive globules, shown 
in these figures by the white dots. They are also present in 
the male chromatic substance, but are not so numerous or so 
large as in the case of the female substance. They always 
show well in material fixed in sublimate-acetic; possibly not 
so clearly in material fixed in sublimate-nitric ; and hardly 
at all in material fixed in Perenyi’s solution. They seem 
larger in the early oogonial stage and become smaller as the 
oogonia increase in size. They disappear from the chromatic 
substance at the oocyte stage. They would seem to correspond 
with the peculiar vacuoles that have been described under a 
number of names in the nucleoli of different oogonial cells. 
In Dinophilus they seem to be very similar to the refractive 
granules of the chromatic substance in Batrachoseps seen 
during spermatogenesis, as described by Eisen ( 4 ). They 
are small, of a light yellow colour, and do not stain with 
iron-haematoxylin. They are also doubtless of the same 
nature as the granules figured iu the nuclei of the oogonial 
cells of some molluscs, by Obst ( 12 ), and in Pholcus by 
Yan Bambeke (1). I shall call them the endoclirornatic 
granules, to use the term applied to them by Eisen ( 4 ). 
In the following paper I shall refer to the two chromatic 
bodies of the oogonial cells, one of which is derived from the 
sperm and the other from the female, as the male and female 
pronucleus respectively. It must be understood, however, 
that while they may be spoken of as pronuclei, they are 
more properly one nucleus divided into two distinct com- 
partments, each of which retains its own individuality, 
although surrounded by a common nuclear membraue. 
Now if one of these pronuclei is derived from the sperm, in 
