Miscellaneous. 271 



A Contribution to the Embryogenjf of the ChalcididsD. 

 By M. L,-E. Henneguy. 



The few observations which have been made upon the development 

 of tlie entomophagous Hymenoptera have shown that the embryo- 

 gcny of those species which have been studied hitherto is charac- 

 terized by the absence of nutritive vitelhis in the ovum, by the 

 existence of a single embryonic envelope differing from the amnion of 

 the other Insecta, and by tlie constitution of the larva. As I have had 

 the opportunity of encountering in some larva) of Stratiomys strujosa 

 several stages in the development of a Chalcid parasite, Smicra 

 clai'ipes, with which Swammerdam was alreadj- acquainted, I think 

 it will be useful, in spite of the numerous gaps which my investiga- 

 tion exhibits, to mention the facts which I have observed. 



In a StratioiHi/s-larya attacked by Smicra we find some fifty ova 

 at different stages of development. The youngest which I have 

 examined measured 150 yu in length by 50 /x in breadth. These ova 

 have the form of an elongated ovoid, terminated at each extremity 

 by an appendix like the finger of a glove. The chorion of the ovum 

 is very delicate and perfectly liomogeneous ; its inner surface is 

 clothed by a cellular membrane, formed of a single layer of little 

 flattened cells. Inside this membrane a clear space, fiUed with 

 fluid, surrounds a solid elongated cellular mass, which results from 

 the total segmentation of the formative vitellus. The cellular 

 membrane probably owes its origin to a very precocious differentia- 

 tion of the periphery of the segmented vitellus, and constitutes an 

 embryonic membrane which is comparable to that of the Scorpions 

 and of Poh/xemis. 



The ovum, in consequence of progressive development, increases 

 in volume : its chorion becomes distended ; the appendices shaped 

 like the finger of a glove disappear almost entirely, and are only 

 represented by two little points which are scarcely visible. At the 

 same time the embryonic membrane increases in area, but without 

 the multiplication of its cells. The latter become cularged by 

 flattening themselves out more and more ; they attain very great 

 dimensions, and each possess a nucleus of considerable bulk. 



During the growth of the ovum the central cellular mass becomes 

 hollowed out and differentiates by delamination into two layers, one 

 of which is ectodermic, the other endodermic. The nervous system 

 is formed on the ventral face by two ectodermic thickenings, situated 

 on each side of the median line. At the same time between the two 

 primitive layers of the blastoderm mesodermic elements appear, the 

 origin of which I have not been able to determine. The segments 

 of the body become visible ; the cephalic portion is slightly larger 

 than the rest of the body, and exhibits in front a little papilla, on 

 which the mouth-parts will sul)se(iuently appear. 



At this point the ovum is about GOO ^ in length by 420 ft in 

 breadth ; i< has become about two hundred timers larger than it was 

 at first. The embryonic membrane, which is separated from the 



