378 Vmversittj of California Publications in Zoology [Vol. 16 



SUMMARY 



The following- seem to be the cardinal points in the division of the 

 spermatocj'tes : 



1. In the primary spei'matocyti' there are twenty chromosomes, 

 which correspond in number, shape, and seemingly in size variation, to 

 those found in the mouse egg. 



2. In the first division all of the chromosomes divide. 



3. In the secondary spermatocytes some sections show only nine- 

 teen chromosomes, while others show nineteen in one plane or focus 

 and one in another. 



4. There is one chromosome whicli does not divide in the second 

 division, but passes in advance toward one pole of the spindle. 



5. There is no secondary pairing of the chromosomes such as has 

 been described in the hoi-se, pig, guinea-pig, opossum, and in man. 



6. The spermatids are dimorphic, half having nineteen, and half 

 having twenty chromosomes. 



'rransmitted October 30, 1016. 



Zoological Labor.vtory, 



University of California. 



