Zoology. — "Secondary sex-characters and testis of the ten-spined 

 Stickleback {Gasterosteus pn,)h/i/iHs L.)." By Dr. G. J. van 

 OoKDT. (Commaiiicated by Prof. J. Boeke). 



(Communicated at the meeting of March 24, 1923) 



It is generally known that the sex-glands strongly intiuence the 

 so-called secondary sex-characters. This is apparent from the maiked 

 somatic and psychic differences, which e. g. Mammals or Birds, 

 castrated at an e&v\y age, show, when compared with normal 

 animals. 



At present it is generally accepted that in Vertebrates this effect, 

 resulting from the gonads, takes place by internal secretion, that is 

 by the influence of certain substances, which pass into the blood 

 ("hormones"). As the correlation between the secondary sex-characters 

 and the gonads generally is most distinct in male Vertebrates, I 

 will speak only of the formation of these hormones in the testis 

 for convenience' sake. 



Recently it has been especially attempted to ascertain, by which 

 part of the male gonad these hormones are formed. The nnmerous 

 investigators, treating this subject, chiefly hold the two following, 

 contradictory opinions. 



According to Stieve (1922) and others these hormones are exclu- 

 sively formed by the sexual cells, whereas Bouin and Ancel(1903), 

 Steinach (1920), LiPscHtJTZ (1919), Bascom (1923), their collaborators 

 and others are of opinion that these hormones originate in the 

 interstitial cells (Leydig's cells), situated in the interstitium of the 

 male gonad. According to Stieve these cells are only thropic ele- 

 ments for the sperm cells. Consequently no value must be attached 

 to the name ,, Puberty Gland", which name was given to the col- 

 lective Leydig's cells by Stkinach and Lipschütz. 



Up till now the investigators, when treating the subject above 

 mentioned, have chiefly examined Mammals, Birds and Amphibia. 

 For that reason I resolved to trace the changes in the testis at the 

 appearance of the secondary sex-characters in a Fish, and so I 

 chose the ten-spined Stickleback (Gasterosteus pungitius L.), 

 which was easy to obtain. 



During breeding time, in spring, the males of this species possess 



