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SCIENCE. 



[N. S. Vol. XXIV. No. 625. 



millimeter in length and has taken the form 

 of a sausage, there are about forty muriform 

 bodies in the interior, all distinct from each 

 other and surrounded by the common granular 

 mass. The number of cellules which com- 

 poses them is always somewhat reduced. 



Toward the middle of May the complex 

 polygerm has become a string of from three 

 to four millimeters in length; the gemmules 

 have multiplied until they are often more than 

 a hundred. They have on an average twenty 

 to forty cellules which, by reciprocal pressure, 

 seem polygonal. From this period the em- 

 bryonic buds begin to issue and the form of 

 the body to become fixed. The embryo, aban- 

 doning its spherical form, becomes more dis- 

 coidal and takes on a reniform aspect. This 

 very characteristic form is generally found 

 about the twenty-fifth of May with H. cog- 

 natella. Finally toward the tenth of June, 

 the embryo having passed to the larval condi- 

 tion, the chains of the Encyrtus reach their 

 definite length and show the typical form 

 described at the beginning of this article. 



The most striking fact in the development 

 of the Encyrtus is then that a single egg 

 placed in the egg of the moth proliferates by 

 the division of the nucleus in such a way as 

 to form a certain number of plurinuclear 

 masses, and that these, dividing in their turn, 

 give rise to as many morules as there will be 

 embryos in each of the chains. 



Polyembryony being, as appears from what 

 precedes, the ordinary method of development 

 of Encyrtus fuscicollis, one can predict that 

 the study of the Chalcicidae, especially of the 

 Encyrtinse, will show other analogous cases. 



Marchal cites already Ageniaspis testaceipes 

 Eatz., parasite of Lithocolletis cramerella, a 

 miner of oak leaves. He has been able to see, 

 it is true, only the advanced stages of the 

 evolution of this species, his observation hav- 

 ing been made in the month of October. The 

 larvae to the number of twelve or fifteen to 

 each caterpillar had for the most part already 

 formed their cocoons. But in some cater- 

 pillars the parasites were grouped in an epi- 

 thelial tube similar to that of E. fuscicollis. 

 The structure of the tube being absolutely 



the same, it is probable that the development 

 goes on in the same way. 



Another case of polyembryony has been ob- 

 served by Marchal: Polygnotus minutus Lin- 

 deman, a minute prototrypid, .5 mm. long, 

 parasite of the Hessian fly. The embryos, 

 which are found to the number of ten to 

 twelve in the gastric sac of the larva of the 

 Hessian fly, are grouped in such a manner 

 as to form a single ovoid mass. 



The author, it is true, has not observed the 

 Polygnotus in the act of oviposition, but, 

 having found freshly-laid eggs in the gastric 

 cavity, he has succeeded in following the mul- 

 tiplication of the nuclei, then the grouping of 

 the cellules in several individuals as distinctly 

 as with the Encyrtus. Polyembryony is then 

 well established for this species. The only 

 differences from Encyrtus fuscicollis are, first, 

 that to the morula stage succeeds a true blas- 

 tula with a central cavity before the forma- 

 tion of the embryo ; second, that the prolifera- 

 tion of the germ being much less active, the 

 number of individuals issuing from the egg 

 does not appear to exceed twelve. 



Following the publication of this remark- 

 able paper, the subject of polyembryony was 

 taken up by Dr. Filippo Silvestri, of the 

 Royale Scuola Superiore di Agricoltura, at 

 Portici, Italy, who published in 1905 a paper 

 entitled ' Uno Nuovo Interessantissimo Caso 

 di Germinogonia,' etc. (Rendiconti della R. 

 Accademia dei Lincei, Vol. XIV., 2d sen., 

 Serie 5% fac. 10°), which consisted of a pre- 

 liminary note on the study of polyembryony 

 with Litomasiix truncdtellus, the same species 

 which had been observed by the writer and by 

 Giard. 



In 1906, in a paper entitled ' Contribuzioni 

 alia Conoscenza Biologica degli Imenotteri 

 Parassiti,' ^ the same writer, Silvestri, goes 

 into detail, with text figures and plates, re- 

 garding a most interesting series of observa- 

 tions, in which he sums up practically as 

 follows : 



Litomasiix truncatellus lays its egg in the 

 egg of Plusia gamma. 



* 1. Biologia del Litomastix truncatellus 

 (Dalm.) ; 2d. Nota Preliminare, Portici, 1906, 

 pp. 1-45, pi. I.-V. 



