OOGENESIS AND EARLY EMBRYOLOGY ASCARIS 573 



may not have theoretical importance for the question, is the 

 behavior of the chromosomes of the sex cells after the soma cells 

 have been definitely separated from them. In these cells, re- 

 sulting from the division of the sixth generation of stem cells, 

 the chromosomes (fig. A, 11) gradually lose their dyad appear- 

 ance and become ovoid monads. They have the same appear- 

 ance when first recognized in the spermatogonia and oogonia, 

 which appear in the young individuals soon after hatching. It 

 seems to the writer that this disappearance of the Querkerbe has 

 no real significance, as the structure always reappears before the 

 oogonia or spermatogonia undergo further development, and 

 hence the physiological potentiality of the Querkerbe is always 

 present, even if it is morphologically^ lost to view. The same 

 argument can not be applied to the soma cells, for the Querkerbe 

 never reappears in any of them. They are always characterized 

 by the larger number (sixty to seventy-two) of small, spheroidal 

 chromosomes, thus showing that not only the morphological, 

 but also the physiological identity of the Querkerbe is lost. 



There is another possible interpretation of the Querkerbe, viz., 

 that it is the indicator of the plane along which the chromosomes 

 will be divided at the time they undergo the process of ' diminu- 

 tion.' This interpretation, however, is open to the very serious 

 objection that the Querkerbe is present in forms which do not 

 undergo a process even comparable to 'diminution;' therefore, 

 although it is possible that such an interpretation might hold 

 among the nematodes, it is highly improbable that it could be 

 accepted in any other group of animals. 



Another question brought to our attention by this study is 

 that of the origin and the behavior of the centrosome 'couple' 

 which functions in connection with the first cleavage spindle. 

 From the study of the spermatogenesis of A. canis, we find that 

 the sperm brings into the egg at the time of its entrance a cen- 

 trosome, imbedded in its nuclear substance, and also that this 

 centrosome soon becomes released from the sperm and lies free 

 in the egg cytoplasm. The present case is of considerable in- 

 terest because it is one of the few instances in which the male 

 centrosome has been definitely followed, first, in the spermatid 



