20 MARGARET MORRIS 



This process of fusion of the first polar nucleus and the egg 

 nucleus is characteristic of the experiments from which larvae 

 develop, and the stages described above are of common occur- 

 rence. There are, moreover, no evidences of any other method 

 of development in eggs which have no polar bodies. Up to a 

 late stage of the development of the cultures, eggs are found in 

 the preserved material in which the first polar spindle in meta- 

 phase still occupies the center of the egg. These have evidently 

 not responded at all to the parthenogenetic treatment, and they 

 go to pieces without having advanced beyond this condition. 



b. Cleavage and development to larvae. The preparations for 

 the first cleavage in the eggs without polar bodies are not abnor- 

 mal except for the absence of the asters, which do not appear 

 till late in the cleavage and are never very large. In the stage 

 represented in figure 61 the chromatic material has begun to 

 condense, in irregular masses, and later (fig. 62) definite threads 

 are to be seen. 



One would naturally expect to find thirty-six chromosomes 

 in the equatorial plate of the first cleavage of one of these eggs, 

 since thirty-six daughter-chromosomes went to make up the 

 cleavage nucleus. When the plates are examined, however, they 

 are found to contain fifty or sixty chromosomes apiece. These 

 have not the form characteristic of the chromosomes of the 

 first cleavages of the fertihzed eggs. Instead of being threads, 

 they are compact rods, not much more than half the size of 

 the normal cleavage chromosomes (figs. 63 to 65). They are, 

 in fact, much more like the rods found in the late cleavages of 

 the normal egg (cf. fig. 16). In the metaphase of the first 

 cleavage the chromosomes form a plate or a ring and there is 

 little difficulty in counting them. The number is not constant: 

 of the three plates represented in figures 63, 64 and 65 one has 

 fifty-six, another fifty-eight and the third sixty-one chromo- 

 somes. It seems probable that there has been an abnormal dis- 

 tribution of the chromatic material into fifty-five or sixty small 

 rods instead of thirty-six threads. Were the number of rods 

 seventy-two one might suppose the daughter-chromosomes of 

 the first polar spindle to have been bivalent, but there seems to 



