404 EDITH PINNEY 



2. Fundulus heteroclitus 9 X Prionotus carolinus cf 



In this combination there is the same abnormal behavior 

 on the part of the sperm chromatin in the early mitoses that is 

 seen in the cross just described. Figures 5 to 8, inclusive, show 

 first and second cleavage anaphases. All of the chromosomes 

 crowded at the ends of the spindle could not be included in 

 the drawing without altering their spatial relations. The lag- 

 ging chromatin, however, has been depicted as accurately as is 

 possible with such minute objects. There can be no doubt that 

 here again we would obtain a great range in variation in the 

 chromatin content of early blastomeres. As before, the second 

 cleavage anaphase repeats the abnormal behavior of the first. 



Observations upon the prophase stages of the first cleavage 

 were not made, but it seems reasonable to assume that they 

 resemble the prophase stages of the second cleavage. After 

 the first cleavage two normal-appearing nuclei are reformed, the 

 centrosome divides, the asters which are to function in the second 

 cleavage appear, and their growth proceeds normally. This 

 process is beautifully clear in the Fundulus egg. That the rays 

 of the aster are formed by the rearrangement of the cytoplasmic 

 reticulum, as described by Wilson (17) for the sea-urchin egg, 

 is quite obvious, and one feels convinced that, however much 

 the structural appearances in fixed material differ from the actual 

 state of the living egg, the relation between astral system and 

 cytoplasm is the same in both. When the astral rays have ex- 

 tended well out into the cytoplasm, approximately half-way to 

 the cell wall, division of the chromatin, which meanwhile has 

 formed the equatorial plate, begins. It is during this ensuing ana- 

 phase stage that abnormahties arise. The point I wish to make 

 is that if the second anaphase which is abnormal is preceded by 

 perfectly normal processes as far back as the first anaphase 

 which was likewise abnormal, then we may assume that it in 

 turn is preceded by a normal prophase. Morris gives figures 

 which show the early stages preceding the first cleavage ana- 

 phase in the cross Fundulus 9 X Ctenolabrus cf to be normal 

 (11). The same sort of observations were made by Godlewski 



I 



