148 



ALICE M. BORING. 



tubules and the count of cells includes the triangular space 

 between three tubules. There is very little difference in the 

 space width of 147 and 2323, but the triangles of 2323 are de- 

 cidedly smaller. 



This difference in tubule size is so striking and seems so 

 strange in birds so nearly alike in other ways, that I tried to 

 find any possible other explanation than that of individual varia- 

 tion. It occurred to me that possibly the size of tubules might 

 vary in different parts of the testes, and as the pieces of testes 

 first sectioned were cut out of the organ without any reference 

 to position the probability is that they were from different parts 

 in the four different testes. However, in two birds killed, I 

 carefully fixed pieces from the periphery and from the center 

 of the organ, as these two regions would represent any difference 

 in pressure conditions or in growth. The sections of these pieces 



FIG. 5. Triangular space of interstitial tissue in cf 666, showing many nuclei 

 of different shapes and staining capacity, also many fat globules arranged in rows. 

 X 1,000. 



show that the tubule size is the same throughout. Though the 

 testis from which Fig. 3 is drawn has many fully formed sperma- 

 tozoa, it is just possible that it has not reached the climax of 

 growth, and would eventually have contained tubules as large 

 as those in Fig. 4. 



In the adult testis, the nuclei vary in shape exactly as in the 



