DENDEOSOMA EADIANS, EHEENBERCt. 
159 
The minute structure of the resting micronuclei is very 
difficult to determine as they stain so deeply; but we have 
satisfied ourselves that there is a definite nuclear membrane 
and a network of chromatin (figs. 22, 23). 
The resting micronuclei are always spherical in form. 
When seen in pairs and clusters they are about 3'3,u in 
diameter; when isolated they are sometimes as large as 4‘5/tt 
in diameter. Various stages in the division of the micro- 
nucleus have been observed, but others are missing. Our 
account of the process is not, therefore, quite complete. 
What we have seen may be regarded as a modified form of 
mitosis. It cannot be positively asserted that a more direct 
mode of division of the micronuclei does not take place, but 
as the different stages of division have been seen in areas 
where gemmule foiunation has begun, and also in areas where 
there is no evidence that gemmule formation is about to take 
place, and as, moreover, we have never seen any signs of 
direct division in the hundreds of micronuclei we have 
examined, it seems probable that amitotic division of the 
micronuclei never occurs. 
The history of the mitosis so far as we can judge at present 
is as follows : The micronucleus swells and then becomes 
slightly oval in outline (fig. 24). The smallest specimen we 
have seen at this stage is 9%3 p by 5T ,u. It is difficult to 
determine whether the chromatin network has broken down 
at this stage or not, but definite lines can be distinguished 
running in the direction of the longer diameter. In the 
next stage the oval shape is changed to a spindle shape and 
the size is 15‘3/i by 6'8p (fig. 2(1). 'Phe chromatin seems to 
be withdrawn from the points of the spindle, which are 
usually quite clear at this stage. The chromatin is in the 
form of a large number of minute granules connected by a 
network of fibrils. It is possible that Ave have missed a 
stage here, as we have not found a spindle form yet with the 
chromatin collected together more definitely into an equa- 
torial band. 
We have found three or four examples of a stage in the 
