xi REPRODUCTIVE ORGANS AND THE FAT BODIES 217 



of the spermatozoa the testes of the frog assume a different 

 appearance in different times of the year. In Rana fusca, 

 according to Nussbaum and Ploetz, the testes are smallest 

 in May, after they have discharged their spermatozoa. Then 

 they gradually increase in size until August, when they attain 

 their maximum, after which they decrease in size during the 

 fall and less rapidly during the winter. In Rana escuknta, 

 according to Ploetz, the testes vary little in size in different 

 months. This is, perhaps, due to the fact that during most 

 of the year all stages of spermatogenesis may be met with 

 in some of the tubules. The interstitial substance between 

 the tubules increases in Rana fusca from March to Septem- 

 ber. There is a storage of fat and pigment during this 

 period which later disappears (Ploetz, Friedmann). In 

 Rana esculenta there is most interstitial substance around 

 those tubules in which the process of sperm production is 

 most rapidly going on. 



The Fat Bodies (Corpora Adiposa).- The fat body is a 

 yellowish organ lying just in front of the gonads. It is fur- 

 nished with a number of finger-like processes whose number 

 varies not only in different individuals but also in the same 

 individual at different times. In the male the fat body is 

 broadly and closely attached to the anterior end of the 

 testis. In the female it is less closely attached to the gonad 

 than in the male. 



The fat bodies serve as a sort of storehouse of nutriment. 

 They undergo great changes in size during different seasons 

 of the year, as has been described in a previous chapter. 

 The histological phenomena which accompany these changes 

 have been studied by Toldt, Neumann, and Giglio-Tos. In 

 the spring nearly all of the fat disappears from the cells 

 (Toldt), and as there are usually two or more nuclei in each 

 cell at this time, it is probable that cell division takes place- 



