Influence of the Primary Reproductive Organs. 603 



in the egg) and in the case of the silkworm moth, at least, become 

 obviously differentiated as ovaries or testes long before the sec- 

 ondary characters have made any beginning at all at differentia- 

 tion. If, therefore, the primjiry organs (ovaries, testes) of a silk- 

 worm could be removed at any time before the last larval moulting, 

 any direct stimulus or influence of these organs on the later devel- 

 oping secondary characters, would be prevented. 



After the experiments described below had been completed 

 my attention was called to the previous experiments of the same 

 nature by Dr. J. Th. Oudemans on the gypsy moth, Ocneria 

 dispar. Dr. Oudemans (in 1895 and 1896) removed variously 

 the right or left or both reproductive organs of larvae of Ocneria 

 and noted that in the moths developed from these larvae no 

 modification whatever of the secondary sexual characters 

 appeared. Of practically all the results obtained by Dr. Oude- 

 mans^ with Ocneria dispar my own observations on Bombyx 

 mart are wholly confirmatory. In the light of the fact that the 

 removal in early life of the reproductive organs of vertebrates 

 affects in marked degree the development of the secondary sexual 

 characteristics, the absence of any such effect in insects (at least 

 in the only ones yet experimented on) introduces to biologists an 

 interesting problem. 



Herbst- suggests that as the primary reproductive organs are 

 differentiated (as to sexual character) early in larval life, their 

 influence on the presumably already developing secondary sexual 

 characters has been exercised before their artificial extirpation. 

 As a matter of fact although the histoblasts of those imaginal 

 organs which show secondary sexual characters as wings, antennae, 

 etc., may in some cases be distinguished from the rest of the larval 

 derm in early larval life, no approximation to actual wings or 

 antennae exist until much later, and no distinction between male 

 and female wings or antennae, etc., until a very late stage in the 

 larval life. In some cases, indeed, the histoblasts are not apparent 

 until a considerable part of the larval life has been passed, while, 

 as I have definitely determined for the silk worm, Bombyx mori, 



iZool. Jahrb. Abt. Syst., 1898, Vol. XII, pp. 71-88. 

 ^Formative Reize, 1901, p. 79. 



