

Fig. 23. Sections of testis of the starling (Sturnus vulgaris), showing the effect of 

 electric lighting added to the bird's normal daily duration of light during the autumn. 

 (After Bissonnette, Physiol. Zool., 4.) (A) Inside young control bird — no light added 

 — kept inside as control for (B) from November 9 to December 13. (B) Inside young 

 experimental bird, receiving additional light from "25 watt" bulb from November 9 to 

 December 13. Total treatment, 34 davs. 









S?"^>>.«<^' *,^v v'^ A. 



s?^^Ml 







... . . i « i^'v^' «*.- 



:.?>' 



v>.. 





Fig. 24. Sections of testis and epididymis, showing modification of sexual cycle in the 

 ferret, Putorius vulgaris, by exposure to increasing periods of light. (After Bissonnette. 

 '35b.) (A) Seminiferous tubules from normal male over 1 year old, made on October 

 3, no lighting. (B) Epididymis of normal male on October 3, no lighting. (C) Seminif- 

 erous tubules of experimental male on November 7, 36 days of added lighting. (D) 

 Epididymis of experimental males on Nov mber 7, 36 days of added lighting. 



45 



