FATE OF UNFERTILIZED EGG IN WHITE MOUSE. 323 



able to carry on the natural processes. The abstrictions of the 

 yolk often look like multicellular structures, but Newman thinks 

 this appearance is due to fixation. Some of these yolk fragments 

 which he calls cytoids contain deutoplasmic granules. 



New r man finds numerous tri- and multipolar spindles. These, 

 he thinks, would result in nests of nuclei without division of the 

 cytoplasm. Sometimes instead of a single resting nucleus formed 

 from the maturation spindle, two nuclei might be formed instead, 

 without the extrusion of the polar body, and suggests that from 

 these double nuclei, the multipolar spindles might be formed. 

 As the number of chromosomes is more tha'n the haploid number 

 such spindles cannot be maturation spindles. In those cells 

 with a true cleavage spindle, Newman is inclined to the view 

 that no polar bodies have been given off. The process is in his 

 opinion a true parthenogenesis, but development does not pro- 

 ceed beyond the eight cell stage and even at that time advancing 

 degenerative processes are to be seen. 



Heape ('05) found that in the domestic rabbit copulation acted 

 as a stimulus to certain internal rearrangements which ended in 

 severing the ovum from its source of nourishment. At about 

 nine hours after copulation the two polar bodies are formed and 

 ovulation takes place about an hour later. He says: "Once 

 freed from the ovary the mature ovum is incapable of assimilating 

 nutriment unless it be fertilized; if from any cause fertilization 

 is not effected, the ovum quickly dies, although it is bathed in 

 the nutrient material supplied by the maternal tissues; ova thus 

 degenerating are from time to time to be seen in the Fallopian 

 tubes." It is therefore necessary for spermatozoa to be at the 

 top of the Fallopian tube because, unlike the condition in the 

 mouse, the ovum is dehisced from the ovary without any discus 

 cells to provide it with food. 



Bonnet ('oo) reviews the different theories of degeneration and 

 takes the view that the various spindles figured by the exponents 

 of the parthenogenetic idea are to be considered more or less 

 abnormal maturation spindles, and not cleavage spindles. 



Van der Stricht ('01), in his study of follicular atresia in the 

 bat, comes to the conclusion that the oocyte of the second order 

 forms a cleavage spindle and divides parthenogenetically. He 



