28 M. Paul Maiclial on Dissociation of 



V. — On the Dissociation of the Egg into a Large Number 

 of Distinct Individuals^ and the Cycle of Development 

 in Encyrtus fuscicoUis {Hymenopteron). By Paul 

 Marchal *. 



In insects asexual reproduction may manifest itself at dif- 

 ferent stages in the ontogeny. Sometimes we find larvai 

 reproducing by budding forth new larvae in the interior 

 of their bodies (pedogenesis) ; sometimes it is a case of 

 adults giving birth to new individuals which develop in the 

 ovaries of the parents (parthenogenesis of the Aphides). We 

 have just discovered in the parasitic Hymenoptera a new 

 mode of reproduction which completes this series of pheno- 

 mena, of which it constitutes, to some extent, the first step ; 

 in Encyrtus fiiscicollis, whicii we have been studying, it is, 

 in point of fact, at the outset of the ontogeny, in the egg 

 itself that the dissociation of the body takes place, and it is 

 at the expense of a single &gg^ that we shall see the formation 

 of a very large number of embryos, which may exceed one 

 hundred, and are all destined to become perfect insects which, 

 at any rate as a rule, will be of the same sex. 



It had already been observed by M. Ed. Bugnion f that 

 the caterpillars of the Hyponomeuta of the spindle- tree might, 

 in the course of June, contain extremely curious chains of 

 parasitic embryos. These chains, only one of which was 

 usually found in each infected caterpillar, were formed on an 

 average of from fifty to one hundred individuals arranged 

 one behind the other, surrounded by a granular mass analo- 

 gous to a vitellus, and united in a long common epithelial tube, 

 which was closed at both ends, and floated in the lymph of 

 the caterpillar by the side of the alimentary canal. Bugnion 

 followed the development of these embryos, and saw that 

 each of them produced a specimen of Encyrtus fuscicoUis. 

 How and where was the oviposition of the Encyrtus per- 

 formed ? Above all, what was the origin and significance of 

 the common epithelial tube enclosing the chain of embryos ? 

 These were questions well calculated to excite the curiosity 

 of the naturalist. In the opinion of M. Bugnion the Encyrtus 

 hatched in summer hibernated, or produced a second genera- 

 tion, the host of which was unknown ; he considered that, at 

 all events, the insect must, during the month of May, deposit 



* Translated by E. E. Austen from the ' Comptes Rendus,' t. cxxvi. 

 no. 9 (Feb. 28, 1898), pp. 662-664. 



t Ed. Bugnion, " Recherches sur le d6veloppement postembryonnaire, 

 I'anatomie et les nioeiu-s de VEncyrtus fuscicoUis " (Recueil zoologique 

 Suisse, t. V. pp. 435-535, 1891). 



