244 ENTOMOLOGICAL NEWS. [Sept., '05 



fifty to a hundred or more within a transparent, flexous tube floating in 

 the lymph. This tube, which is usually branched, is formed by a struc- 

 tureless membrane lined by a layer of epithelioid cells. The larvae hatch, 

 live for a time free in the body cavity of the host, then pupate within 

 little cells and finally emerge as adults early in July. Bugnion was 

 unable to observe oviposition but thought that the eggs were deposited 

 en masse. He at first supposed that the embryo-tube was formed from a 

 secretion of the mother, but on observing its epithelioid nature he decided 

 that it represented the fused amnia, or embryonic envelopes. He was 

 unable to account for the disappearance of the choria, or shells, of the 

 fifty or more eggs, since he found no trace of them. Though the adults 

 paired soon after emergence, he considered that they hibernated and 

 oviposited in the young caterpillars of the following spring. 



The gaps in the woik of Bugnion were filled, and the correct interpre- 

 tation of some of his observations was made possible by the researches 

 of Marchal. This investigator found that the adult parasites did not 

 hibernate but that very soon after emergence they deposited a single egg 

 within that of the host. This process required from >^ to 2 minutes, and 

 the female might remain for an hour or more on a single mass, passing 

 from one egg to another. On sectioning and staining the egg-mass of 

 the moth, Marchal was able to find a single egg of the parasite within that 

 of the host. This egg, instead of developing in the usual manner, be- 

 comes broken up into a great number of small morulas, each of which 

 develops independently within the common envelope. This envelope he 

 found to be of adventitious origin, formed from cells of the host. Many 

 stages in the dissociation of the egg were followed, and are described in 

 such detail as to leave no room for questioning the accuracy of the obser- 

 vations. The phenomenon was observed not only in the Chalcid Ageni- 

 aspis but also in the Proctotrupid Polygnotus minuius parasitic upon 

 larvae of the Hessian-fly. As Giard suggests there is little doubt that 

 polyembryony will be found to occur also in such cases as those cited by 

 him and Pergande. 



In this polyembryony we have a phenomenon entirely unsuspected for 

 the Arthropods. Indeed, it is not exactly paralelled in any group of 

 animals though similar instances have been reported for some of the 

 Bryozoa. Cases of parthenogenesis are not rare among mature insects. 

 Rarely we even meet with asexual reproduction by immature forms 

 (paedogenesis by pupae of a Chironomid, and by larvae of a Cecidomyid) 

 but in the cases reported by Marchal we have parthenogenetic multipli- 

 cation in the early egg-stage — the extreme of this type of reproduction. 



The broad biological interest of these discoveries is just being realized. 

 Their bearing on theories of sex determination, on such questions as the 

 origin of twins, and on problems of artificial polyembryony are among 

 those which are being discussed. Marchal's work affords a new stimulus 

 to the study of insect parasites, and we may expect a rapid increase in 

 our knowledge of the development of these interesting forms. — William 

 A. Riley. 



