312 POLYEMBRYONY AND THE DETERMINATION OF SEX. 



egg masses of II. maluilelxlelht.^ and having fixed tliem in Gilson 

 liquid, stained them with carmine, and cut them into fine sections, he 

 succeeded in discovering the ^gg of Encyrtus included within the 

 general cavity of an already large and advanced embryo of Hypo- 

 nomeuta. The egg is so minute in size that, at the most, one can 

 not make a series of more than four to five sections including its 

 substance. Its contour is ovoid, clearly defined, and one can not see 

 the least trace of the eggshell and the pedicle observed before ovipo- 

 sition. There are in its interior five nuclei immersed in the as yet 

 undivided protoplasmic mass, of which four are smaller, rounded, 

 alike among themselves, and one more voluminous placed eccentric- 

 ally, of irregularly lobed form, presenting a very fine and very 

 dense reticulation. We will state further that the four small nuclei 

 (embryonal nuclei) are destined to produce by successive prolifera- 

 tion the entire chain of embryos, while the larger nucleus (para- 

 nucleus or amniotic n.) constitutes the first formation of the 

 amnios. 



At this stage the egg of Encyrtus is not inclosed in any membrane ; 

 one onh^ perceives in its vicinity the presence of some mesenchyma- 

 tous cells, which belong to the host. It is a little later, wdien the 

 number of embryonal nuclei has increased to 8 or 10, that an adven- 

 titious cyst begins to form by the drawing near of the mesenchyma- 

 tous elements, which press against the egg, and thus form a lining 

 of flattened cells. As to the amniotic cells derived from the para- 

 nucleus, their role is to form the albumino fatty body which con- 

 tains the embr3'os and which is soon to serve for the alimentation 

 of the 3'oung larvae. 



At the end of September the little caterpillars hatch, but they 

 confine themselves to gnawing the remains of the eggs and rest until 

 spring beneath the carapace which covers them. In examining these 

 caterpillars under the microscope, one can perceive among certain of 

 them the presence of one and sometimes two or three small rounded 

 bodies, still difficult to distinguish, floating among the viscera. These 

 little bodies, which are the eggs of Encyrtus inclosed in their cyst, 

 may be studied at the time both by picking to pieces in water with 

 osmic acid and by the method of sectioning. Examined by trans- 

 parency at the end of autumn, the egg offers a mass of ovoid or 

 globular protoplasm in which are immersed, first, a mass of embryo- 

 nal nuclei pressed one against the other, to the number of 15 or 20; 

 second, a large paranucleus placed eccentricall}^, sometimes divided 

 into two segments. 



The stage wdiich has been described persists nearly without modifi- 

 cation throughout the winter. However, in a goodly number of eggs 

 one can perceive from the middle of March and even of February a 



