NUMBER AND BEHAVIOR OF THE CHROMOSOMES 



IN CAVIA COBAYA 1 (THE COMMON 



GUINEA PIG). 



MARY T. HARMAN AND FRANK P. ROOT. 



KANSAS STATE AGRICULTURAL COLLEGE. 2 



INTRODUCTION 



MATERIAL AND METHODS. ... -4 



DESCRIPTION OF MATERIAL 



1. Spermatogonial divisions 75 



2. The growth period 



3. Spermatocyte divisions 7 6 



DISCUSSION 



SUMMARY -p 



LITERATURE CITED 7O , 



DESCRIPTION OF PLATES 82 



INTRODUCTION. 



Since the guinea pig has been used extensively in genetic 

 experiments and since investigation has revealed in many in- 

 stances a close correlation between the genetic behavior and the 

 number and behavior of the chromosomes of many organisms, 

 the number and behavior of the chromosomes of the guinea pig 

 is of interest alike to the cytologist and the geneticist. 



According to Harvey (1920) there is a wide difference of opinion 

 concerning the number of chromosomes observed in Cavia. 

 Von Bardeleben (1892) reports sixteen spermatogonial chromo- 

 somes and eight chromosomes in the spermatids. Flemming 

 (1898) says that there are probably twenty-four somatic chromo- 

 somes. Moore and Walker (1906) give the number as thirty- 

 two in the spermatogonial cells and sixteen in the primary and 

 secondary spermatocyte cells. Stevens (1911) says that there 

 are about fifty-six spermatogonial chromosomes and tweni\ 

 eight chromosomes in both the primary and secondary spermatu- 



1 Dr. H. L. Ibsen furnished the guinea pigs for this study. P. VV. Gregory 

 assisted in the fixation and dehydration. The drawings were made by I 



Prince. 



2 Contribution from the Zoological Laboratory, Kansas State Agricuhma! 



College No. 851. 



73 



