TRYPANOSOMA 



387 



The development of Schizotrypanum differs in many points from 

 this description, for the trypanosome enters an endothelial cell in 

 the lung, or a cardiac muscle fibre, or a neuroglia cell of the central 

 nervous system, or a striped muscular fibre. In these situations it 

 becomes simply a rounded body, which possesses trophonucleus and 

 kinetonucleus, but has lost its flagellum and undulating membrane. 

 This body undergoes repeated divisions, and each division eventua- 

 ally becomes a trypanosome. 



In the Invertebrate Host. — -Theoretically, it would be expected 

 that sexual forms, male and female, would be found in the blood of 

 the vertebrate, and that these, taken into the alimentary canal of the 

 blood-sucker, would conjugate and produce ookinetes, and perhaps 

 oocysts, from which forms would be produced which might infect 

 the proboscis of the same individual, or, by entering into the eggs, 

 infect a new generation, which alone might be the means of dissemi- 

 nation of the parasite. But these theoretical views have so far not 

 been confirmed by actual observations, which must now be discussed 

 seriatim . 



So-called Sexual Forms. — According to Prowazek, T. lewisi can 

 be differentiated into three forms — (i) male, (2) female, (3) in- 

 different ; and, according to Prowazek, Liihe, Nocht, and Mayer, 

 the same can be seen in T. castellanii ; but according to Holmes, only 

 males, females, and young females can be seen in T. evansi. 



Male Forms.— These are defined to be very slender trypanosomes, 

 actively motile, with an elongated nucleus, which stains well. 



Female Forms. — -Broad, sluggish trypanosomes, with reticulated 

 protoplasm and a round nucleus, both of which stain poorly. They 

 possess a slender, undulating membrane and a short flagellum. 



Indifferent F orms .—These are the forms most commonly met with, 

 possessing granular cytoplasm and a not very well-defined nucleus. 



It must be admitted that between these there are all stages of 

 intermediary forms, so that they are not sharply defined ; and some 

 of these may be simply the ordinary trypanosome in various stages 

 of growth and division, as described above. 



Miss Robertson has probably arrived at the truth when she says 

 that the short forms (13-20 microns) of T. castellanii, the so-called 

 female forms, are really the adults, which by growth become the 

 indifferent forms which are merely steps in the formation of the 

 slender forms, so-called male forms, which are the dividing stage 

 of this trypanosome. 



Chagas has shown that Schizotrypanum cruzi in the lungs may 

 lose its flagellum and become curved into an arc, the extremities 

 of which fuse, forming at first a ring, which subsequently becomes 

 a sphere, with a trophonucleus and a kinetonucleus, the latter of 

 which is expelled in female forms, while it is retained in male forms. 

 In this manner the macrogametocytes and the microgametocytes 

 arise. Each of these divides into eight macrogametes, which are 

 uninuclear, and eight microgametes, which have a trophonucleus 

 and kinetonucleus united by a filament. These gametes escape from 



