Maturation and Fertilization in Theridium. 247 



ficial nuclei contain the reduced number of chromosomes. In each 

 of two eg-gs of the 4cell stage, with all four cleavage nuclei adcentral, 

 two of these excentric mitoses were found widely separated from 

 each other; therefore since there can be only one second polar 

 body, one of these two excentric division figures must be that of a 

 supernumerary sperm. Save for the difference in the number of 

 chromosomes these mitoses resemble those of the cleavage nuclei 

 and do not appear abnormal in any respect, so that it is quite 

 possible that certain cells of the later blastoderm might descend 

 from supernumerary sperm nuclei. In such a case most of the cells 

 would have the double set of chromosomes, the one paternal and 

 the other maternal, but some would have paternal chromosomes 

 only; such a condition might well result in marked somatic varia- 

 tion, and this is a possible factor that seems to have escaped 

 attention. 



