PRODUCTION OF SPERMATOZOA IN ROTIFERS. 313 



the other kind are small, immotile and probably rudimentary, and 

 without function. The rudimentary spermatozoa must necess- 

 sarily develop directly from the secondary spermatocytes without 

 the occurrence of the second spermatocyte division in order to 

 form the ratio of two normal spermatozoa to one rudimentary 

 spermatozoon. If they developed from rudimentary spermatids 

 which were formed by the division of the secondary spermatocytes 

 the ratio would be one functional spermatozoon to one rudimentary 

 spermatozoon. This interpretation of the observed ratios would 

 therefore place the rotifers in the same category as the other 

 animals already mentioned as far as the formation of normal 

 spermatids and of rudimentary secondary spermatocytes are con- 

 cerned. They would, however, have this point of difference, viz. : 

 that the degree of degeneration of these rudimentary secondary 

 spermatocytes has not progressed as far as to render such 

 spermatocytes incapable of developing directly into degenerate 

 spermatids and spermatozoa of a certain kind, as is the case of the 

 other forms studied. 



In the mature parthenogenetic egg that develops into the male 

 individual there is the reduced number of chromosomes. This 

 contains one half as many chromosomes as are found in the par- 

 thenogenetic egg that develops' into the female. This fact was 

 made out in Hydatina senta but the exact number of chromosomes 

 occurring in each kind of egg has never been determined. If 

 the male in the beginning has already the reduced number of 

 chromosomes no further reduction of chromosomes is necessary 

 in the formation of the spermatozoa. The race, however, may 

 have retained the former ancestral process of performing the first 

 spermatocyte division, regardless of the results, in the formation 

 of the secondary spermatocytes but as there is no general reduc- 

 tion of chromosomes to be made at this stage presumably none 

 occurs. One half of the secondary spermatocytes very likely 

 contain fewer or perhaps no chromosomes at all and conse- 

 quently are very degenerate and rudimentary and without a 

 second division develop directly into degenerate spermatids and 

 spermatozoa. 



The male parthenogenetic eggs are the ones that are fertilized 

 as has been determined by Maupas, Lauterborn, Whitney, and 



