POLYEMBRYONY AND THE DETERMINATION OF SEX.° 



Resnnir of tile (iltservatioiis of V. Marclial.* 

 Ry E. Ru(!MioN. 



Polijemhryony is the spontaneous division of the g-erni into a num- 

 ber of distinct individuals/ 



Hardly more than a glimpse into a new epoch, this phenomenon, 

 of the highest scientific interest, was observed during the past sum- 

 mer hy Paul Marchal, professor at the Agronomic Institute of Paris, 

 in parasitic Hymenoptera of the genera Eneyrtus and Polygnotus 

 and recognized by this same author as being the normal mode of 

 reproduction of these insects. 



Let us first consider Eneyrtus fnscteoUift Dalman. Scarcely a 

 millimeter in length, this minute Chalcid develops as an endoparasite 

 at the expense of a number of species of moths or Ilyponomeutas (//. 

 cognatella or evonymi of the spindle tree, malialehdella or 'padi of 

 the mahaleb or plum of Santa Lucia, padella of the hawthorn and 

 sloe tree, malinella of the apple.) 



If one examines under the microscope the caterpillars of Hypono- 

 menta (for example, 11. cognatella) at the end of April or during 

 the first half of May, one finds nearly always, or at least among some 

 of them, those with embryos (and later with larvae) of Eneyrtus 

 associated in the form of chains or rows. 



These chains, which I have already described in the Recueil zoo- 

 logique Suisse, v. V, 1891, are composed of 50 to 100, or even 120, 

 individuals. The sac which contains the parasites presents itself 

 as a whitish tube, sometimes bi- or tri- furcate, flexible, folded upon 

 itself, floating in the lymph of the caterpillar outside of the intestine. 

 Formed of an envoloping membrane (cuticle), it is clothed interiorly 



a See the works cited: Marchal, 1807. 1898. 1899, 1903, 1904, and 1904a (prin- 

 cipal memoir). 



6 Translated, by permission, from Rulletin d© la Societe Vaudoise des Sciences 

 Natnrelles, .5 ser., Vol. XLII. No. 1."m, March, 1900. 



c Brandes (1898) proposed, in place of polyembryony, the term gcrniinoffonif. 

 One could also say simntancoiis hlastotomy, 



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