KEMARKS OX THE BAG-WORM. 83 



all the genital parts expanded; k, the fixed outer sheath;/, the 

 clasps ; g, a pale membranous sheath, upon which the praeputium 

 (Ji) plays, as on the finger of a glove ; /, the fleshy elastic penis, 

 armed with retorse hairs, and capable of extending to nearly one- 

 fourth of an inch ; y, showing the end still more fully enlarged. 

 With this exposition of details, not easily observed or generally 

 understood, the act of fecundation is no longer a mystery. 



"Experiments made in 1878 led me to conclude that partheno- 

 genesis, although not improbable, seldom occurred in this species. 

 In some sixty instances where I excluded the males, the females 

 either worked out of their follicles and dropped to the ground 

 without ovipositing, or else died and dried up in the ends of the 

 same, likewise without laying. I have found the same to hold true 

 in those exceptional cases (four have already come under my notice) 

 where, in a state of nature out of doors, the larva had undergone 

 its transformations head upward. In every instance the poor female 

 had worked out of the puparium and butted against the closed end 

 of the follicle, perishing finally without laying, because the male 

 could not reach her.* 



" The impregnated female that has laid her eggs always works out 

 of her follicle when her task is completed, and drops to the ground 

 exhausted ; but she may at once be distinguished from those which 

 perish without ovipositing by her shrunken, eggless body. 



" The fawn-colored down, which the female intermingles with 

 her eggs, is composed of the silky hair rubbed from her body. If 

 examined while yet in the puparium, and just before she would 

 naturally issue therefrom, each ring of the body of the female is 

 seen to be more or less clothed with this silky material, while the 

 eggs are perfectly free from it until they are laid. Under the 

 microscope, this covering is seen to consist of the most delicate 

 fibres, many times finer than ordinary silk, and it is so easily de- 

 tached that most of it rubs off and remains in the puparium on the 

 partial issuing therefrom of the female." 



* Since this was written more elaborate experiments have fully determined that 

 parthenogenesis does occasionally occur in the species. 



