PARTHENOGENESIS 



163 



and are killed off; so, too, are the indifferent forms, but the female 

 cells, being much hardier, continue to live apparently upon the stored 

 up products of a nutritive character. The protoplasm finally becomes 

 vacuolar and the kinetonucleus migrates to a position alongside of 

 the trophonucleus (Fig. 71). Each nucleus then divides, the latter 

 equally, the former by a heteropolar mitosis, which gives rise to a much 

 smaller nucleus and a larger one (A, B). This smaller nucleus, like 

 the kinetonucleus, then divides, equally, one of the daughter nuclei of 

 this division degenerating while the other divides again. The result 

 of this second division is the formation of two nuclei, one of which 

 becomes attached to the larger trophonucleus, while the other degener- 

 ates. The same history is repeated by the products of the kineto- 

 nucleus. One degenerates, while the other divides a second time to 

 furnish a nucleus which similarly unites with the trophonucleus, and one 



FIG. 71 



Parthenogenesis in Trypanosoma noctusD, (After Sehaudinn.) .4, B, approach of the 

 kinetonucleus and division of both nuclei; C, D, division of the kinetonucleus and of the 

 "male" nucleus, degeneration of one-half of each, and union of one-quarter of each with 

 the trophonucleus; E, F, fusion of the two smaller nuclei in the trophonucleus to form the 

 karyosome of the fertilized cell. 



which degenerates (C, D). The two smaller nuclei ("polar bodies") 

 then migrate into the trophonucleus and unite to form a new karyo- 

 some (E, F). With this fertilization the cell is again ready to form 

 other individuals of either male or female type. 



In other trypanosomes similar but not identical processes of 

 parthenogenesis have been described by different observers. Moore 

 and Breinl ('07) describe the union of a portion of the kineto- 

 nucleus in Trijpanosoma gambiense with the trophonucleus, but 

 without any of the divisions, as described by Schaudinn. The 

 kinetonucleus (their "centrosome") grows out into a long rod which 

 reaches the trophonucleus, where a small part is taken into the 

 trophonucleus, uniting with the karyosome. A similar long rod 

 was observed by Prowazek ('05) in Trijpanosoma lewisi, but it was 

 described as arising from the trophonucleus and not from the kineto- 



