z6z 



THE QUARTERLY REVIEW OF BIOLOGY 



operator is essentially destroying all the 

 germinal tissue and that only empty 

 lobules remain. It is further weakened 

 by the fact that the appearance of second- 

 ary sex characters in urodeles just 

 approaching sexual maturity must await 

 the evacuation of the cysts following one 

 spermatogenic cycle, for according to 

 Aron (3, p. nz) only the evacuation of 

 the cysts will introduce the genesis of this 

 endocrine mass. 



Humphrey shows that Aron's abortive 

 spermatogenesis and Champy's presperma- 

 togenesis vary in quantity. They are 

 present only in certain species and not 

 always in these. He draws attention to 

 the fact that in testes of urodeles, as of 

 other vertebrates, unfavorable environ- 

 ment causes injury to the germ cells and 

 their degeneration follows. From data 

 presented (Humphrey, Z3) the conclusion 

 that this germ cell degeneration is the 

 result of unfavorable conditions in winter 

 seems justified. This does not end in the 

 formation of a true anatomical organ, and 

 there is no need to ascribe a definite func- 

 tion to the degenerating lobules or 

 associated interstitial cells. From this 

 alone it cannot be said that the tissue does 

 not perform a function. But if an endo- 

 crine function be ascribed to this tissue it 

 can apply to only a limited number of 

 species, and in these during part of the 

 year. Its limited occurrence makes it 

 seem very improbable that such tissue has 

 an endocrine function in any species. 



MODIFICATIONS IN TESTES OF BIRDS 



In birds the testicular structure re- 

 sembles very much that found in mammals. 

 The germinal tissue is found in semi- 

 niferous tubules, where waves of sperma- 

 togenesis may be seen. The intertubular 

 tissue is composed of lymph and blood 

 vessels, nerves, connective tissue, and 

 some interstitial cells. 



Many early investigators reported volu- 

 metric and weight changes in birds during 

 the year. Gadow (16) refers to the 

 familiar fact that the testis of the house 

 sparrow enlarges from the size of a seed 

 during winter to that of a cherry during 

 the mating season, at which time it dis- 

 places the digestive organs. Disselhorst 

 (14) discusses the increase in volume of 

 the testis approaching the time of mating. 

 In Fringilla there is an increase in weight 

 of about three hundred fold. He also 

 cites Leuchhart as finding an increase in 

 weight of one hundred and ninety fold 

 in the Starling from winter to spring. 

 In these reports, cytological data is 

 lacking and only macroscopic information 

 is given. 



Stieve (3x) reports that in the European : 

 Jackdaw (Colaeus monedula collaris) there : 

 is a fluctuation of four hundred and eight- 

 een volumes in the testis during the year. , 

 This volumetric fluctuation is produced ! 

 by changes in quantity of germinal tissue. . 

 In spring the testes increase in size up to : 

 April. At this time the tubules are : 

 greatly distended with germ cells, and it j 

 is then that mating takes place. There- • 

 after the testes decrease in volume until ! 

 they reach a minimum size in January. 

 The intertubular tissue is most abundant 1 

 when the germ cells are at a minimum 

 during winter. It is most abundant dur- • 

 ing the non-sexual period and least 1 

 abundant at the time of mating. He j 

 refers to the increase in intertubular tissue 

 as an interstitial cell hypertrophy. He 

 is sure that the interstitital cells do not 

 produce the testicular hormone because 

 they are at their minimum when sex activ- 

 ity is at its maximum. 



Parhon and Parhon (2.9) reported that 

 in the goose (of the race Rouen) the 

 testis diminishes in volume about the first 

 of August. The spermatogenic tissue 

 then becomes less abundant, and its cells 



