24 MARGARET MORRIS 



division without cytoplasmic cleavage. Often there is a 3- or a 

 4-cell stage which is normal except for the presence of two nuclei 

 in one of the cells. More abnormal cases are shown in figures 

 38 to 41, where cytoplasmic cleavage is abnormal or entirely 

 lackmg. I have not found stages of mitotic division in the 

 multinucleate cells, and am inchned to believe that the nuclei 

 arise by a process of fragmentation. Their irregular arrange- 

 ment and variable size seems to indicate an entirely abnormal 

 condition. Whether it might lead to differentiation and the 

 foriTiation of unicellular swimmers is not clear. Sometimes the 

 nuclei are arranged peripherally in later stages (fig. 41) and have 

 a fairly normal appearance. These multinucleate cells are 

 found for the most part in experiments in which cleavage was 

 poor and no larvae were formed. 



VI. CYTOLOGICAL STUDY OF EGGS WHICH HAVE FORMED POLAR 



BODIES 



The amount of material preserved from experiments in which 

 a large percentage of eggs formed polar bodies is unfortunately 

 not very great, so that the study of the cytology of these eggs 

 is by no means complete. There are many gaps in the series 

 which must be filled in at some other time. The first stage to be 

 noted in the formation of the first polar body is the early ana- 

 phase represented in figure 69. This is a perfectly normal ana- 

 phase Hke that of the first polar spindle in the fertihzed egg. 

 The cytoplasmic bud is, perhaps, abnormally large, and there 

 seems to be a tendency for this first polar body to have more 

 cytoplasm in the parthenogenetic than in the fertilized egg. 

 The chromosomes, however, behave in a normal way. 



The later stages of this division and the formation of the 

 second polar spindle are unfortunately lacking in the material I 

 have preserved. The next stage to be found is the metaphase 

 of the second maturation. In the case represented in figure 70, 

 the spindle hes unusually far from the periphery of the egg, but 

 instances have been found in which it occupied a normal posi- 

 tion, close beneath the first polar body. The chromosomes of 

 this spindle are hke those of the second maturation of the fer- 



