160 CRESSWELL SHEAEEE. 



schelt has determined in D. apatris, there are two polar bodies given off 

 by both kinds of eggs, the first polar body in tiirn dividing after it has 

 been given off. There are twenty somatic chromosomes. In both eggs 

 there is a regular reduction in the first maturation division, ten dumb- 

 bell shaped chromosomes going out and ten remaining in the egg. In 

 the female egg, however, this process is somewhat different from that 

 in the male, as there seems to be something similar to a synapsis stage 

 in the former which is missed out in the latter. In both eggs after the 

 extrusion of the first polar body, the ten chromosomes remaining in 

 the egg divide, bringing back the number to twenty again. In the 

 second polar body, in the male egg, apparently twenty or eighteen 

 chromosomes go out and the same number remain in the egg. The 

 second maturation division in the female egg, I have been unable to 

 obtain satisfactorily in sections so far, and it may prove that the second 

 polar body in this egg is simply derived from division of the first, and 

 that only one polar liody is actually given off by the female egg. In 

 the first and second segmentation divisions in both eggs there are 

 apparently twenty chromosomes. It is, however, very difficult to 

 make out their number in the male egg very accurately on account of 

 their small size, there are at least eighteen or more, and probably 

 twenty, as in the female egg. 



The details of the maturation divisions I wish to reserve for my full 

 paper on the subject, shortly appearing in the Quarterly Journal of 

 Microscojncal Science. 



