74 



Miss H. L. M. Pixell. 



Multiplication of the Parasite. 



Toxoplasma divides by the simplest form of binary fission. The karyosome 

 elongates and becomes dumb-bell shaped (figs. 16 and 17). The two daughter- 

 karyosomes then move apart from one another, remaining connected by a 

 short centrodesmose (figs. 18 and 19). This soon appears to snap, for it has 

 disappeared by the time the stages represented in figs. 20 and 21 are reached. 

 The vesicle is then constricted off and the two daughter nuclei separate 

 (figs. 22-25). 



Division of the body is usually longitudinal, but may sometimes 

 apparently be transverse, or oblique (fig. 24). Tig. 22 shows two daughter- 

 individuals which have evidently just been formed by longitudinal division, 

 and one appears to be again dividing longitudinally, the other transversely. 



In some infected cells, perhaps owing to the fact that the parasites can 

 divide in different directions, compact more or less spherical masses of 20 or 

 more parasites may be produced which have something the appearance of a 

 cyst. A spherical mass of this kind is seen to be forming at s in fig. 6 and 

 probably also in figs. 4 and 5. The first of these is, however, scarcely half 

 the size of the masses seen in many infected cells. Nicolle (5, p. 99) suggests 

 that this appearance may have led Splendore (9) to interpret erroneously 

 similar masses as cysts in the rabbit. In the schizogony, recently described 

 by Yakimoff and Kohl-Yakimoff (10, p. 202) as taking place in free or 

 intracellular forms, multiple fission into 32 or more may apparently take 

 place, but it is impossible to make out the details of the process from their 

 figures, made from Giemsa preparations. 



Attempts to maize Cultures of the Parasite. 



Attempts were made to cultivate the parasite on agar plates, on blood 

 agar, and in blood serum, also by adding to some peritoneal fluid a small 

 percentage of 50-per-cent. dextrose as recommended by Bass (1) for the 

 cultivation of the Malaria parasite, but in no case could any different form 

 be produced. 



This seems to be all that can be done here in connection with Toxoplasma, 

 but I hope to carry on this work next month in the desert of South Tunisia, 

 which is the most northerly haunt of its natural host — the gondi — and there 

 to investigate its method of transmission and life-history. 



[June 19. — In the above I have purposely refrained from discussing the 

 affinities of Toxoplasma until such time as its life-history should be known, 

 for until then its systematic position must remain uncertain. The parasite 



