384 VERNON L. KELLOGG. 



hatched larvae, but even here the organs are conspicuous and 

 well started in development, being larger in diameter than the 

 heart or the spinning glands. 



We may affirm then positively that from the time of the first 

 moultine on the silkworm larva has its sex determined : its re- 



o 



productive glands are ovaries or testes distinguishable by obvious 

 histologic characteristics. Also that the just hatched larva has 

 reproductive organs already well developed. I have little doubt 

 that careful scrutiny of the organs at this stage would reveal to 

 the trained histologist, especially to the student of oogenesis 



FIG. 8. Section through Bombyx larva (male or female? ), two days after hatch- 

 ing; A, heart; al. c, alimentary canal ; v. n. c, ventral nerve cord ; r, o, reproduc- 

 tive organs. 



and spermatogenesis, definitive characteristics marking sex differ- 

 entiation. The sex of the silkworm is not to be tampered with 

 by gorging or starving, and what is true of this lepidopteron is 

 undoubtedly true of its cousins, the other moths and the butter- 

 flies. It is probably also true of other insects with complete 

 metamorphosis. I recall dissections of various larvoe, notably 

 of Corydalis cornuta (a neuropteron) and of Holorusia rubiginosa 

 (a dipteron) in which the reproductive organs appear of two sizes 

 in specimens of the same age : indeed in Corydalis, of two shapes. 

 These organs need histologic examination. Some student should 

 laboriously work through a long and representative series of in- 

 sects and settle the question as to the time of sex differentiation. 

 That is, find out whether it be true for all, as it is in the silk- 

 worm, that the time of sex differentiation is obvious before, or, 

 at latest, at very little after the time of hatching. If it is true, 

 the question of the influence of nutrition in sex determination 

 will also be settled - - for insects. And we need waste no more 

 time in tedious feeding and tabulating. 



