POLYEMBRYONY AND THE DETERMINATION OF SEX. 313 



grouping: of the embryonal nuclei, which already indicates the divi- 

 sion of the germ into many embryos. The formative vitellus (char- 

 acterized by its clear tint) is divided into many rounded masses, 

 isolated one from the other, each inclosing a group of nuclei. These 

 last, which before had two nucleoles, now present multiple nucleoles, 

 which are arranged in two rows, indicative of an approaching pro- 

 liferation. Some of these are already on the way to kinesis. 



But it is during the period wIimi the 3'oung larva? leave their winter 

 shelter and begin to gnaw the leaves that the phenomena of poly- 

 embryony reach their greatest intensity. 



The egg, at first spherical, grows with an extraordinary rapidity, 

 and little by little assumes an elongate ellipsoid form. It is under 

 this aspect and with a considerably increased diameter that one 

 finds them in the interior of the caterpillars of the spindle tree about 

 the 20th of April. The same stage appears in the caterpillars of the 

 mahaleb about the lOtli of May. 



Examined at this period in thin sections, the germ of the Encj'rtus 

 is found composed of these small rounded masses, which had, in cer- 

 tain cases, commenced to take form at the end of the winter. 



Grown much more numerous, these are formed of small masses of 

 protoplasm, containing the nuclei (to the number of S to 10 in each 

 mass), and already show the cellular limits distinctly enough. Each 

 one of these masses is located in a rounded cavity, with clear-cut out- 

 line, hollowed out in the common granular (nutritive) protoplasm," 

 as with a punch. In order to see the cavity well it is necessary in 

 every case to fix the object with Fleming solution and not with cor- 

 rosive sublimate. It may be colored afterwards with safranine. 

 These bodies, which may be compared to small buds and Avhich we 

 shall hereafter call muriformes, increase by multiplication of their 

 elements; but, arrived at a certain size — each of them made up at the 

 time of 12 to 15 cells — they themselves divide by breaking up. 



During the last days of April, when the polygerminal comj^lex of 

 Encyrtus has attained a half millimeter in length and has taken the 

 form of a sausage, the muriform bodies are present in the interior to 

 about the number of 40, well differentiated from each other and 

 immersed in the common granular mass; the number of cells which 

 compose them is always much reduced, ranging from 8 to 12. 



About the middle of May, at the time when the polygerminal com- 

 plex lias grown into a chain 3 to 4 mm. long, the buds have mul- 

 tiplied to more than a hundred and now constitute the true morules. 

 These have from 20 to 40 cells each, which through mutual pressure 

 on all sides present a polygonal form. From this time on the 

 embryonic lamime begin to unfold and the body begins to take 

 form. The embryo, abandoning the spherical form, tends toward 



