§ 3 



SEXUAL CYCLE OF LEBISTES RETICULATUS 



13 



virgin females were placed in water which had previously 

 contained males, the same thing happened. Evidently some 

 substance is secreted by the males, which stimulates the 

 elevation-position in the females. 



The water in which Lebistes males have been swimming 

 causes growth of the ovipositor in the female bitterling. This 

 is also true of the water which has contained male bitterlings 

 (Fig. 91). Jaski calls the active substance secreted by these 

 male fishes, copulin. 

 A. a 



/o 



hours 



Fig. 91. Ovipositor growth-curves obtained in water activated by Lebistes 

 and Rhodeus males, respectively. 



Following Jaski's investigations, Bretschneider studied 

 the cycle in the pregnant female. In Lebistes, the oocytes, 

 fertilised in the follicle, develop there into young fishes. Preg- 

 nancy lasts about 28 days, and is generally soon followed 

 by another. Lebistes, therefore, is a poly-estrous fish. Since 

 the sperm of one fertilisation serves for more thans one preg- 

 nancy it was not possible to ascertain precisely the moment 

 of fertilisation, for which reason the development of the 

 embryos was used as time-determinant. 



The sperm penetrates the pre-formed stigma of the follicle 

 and enters the mature oocyte, fertilising the latter inside the 

 follicle (Fig. 92). The number of mature oocytes thereby 

 falls to zero; but when pregnancy is only half completed, 

 medium-sized oocytes begin to mature and are ready to be 

 fertilised when pregnancy is completed. The developing 

 ovum is supplied by a rich capillary system in the follicular 



