THE GENUS TRYPANOSOMA 



247 



anterior flagellum and elaboration of the lateral protoplasm into an 

 undulating membrane. According to such a derivation, the flagellated 

 end of a trypanosome would be posterior, and this is the view taken by 

 a number of authorities. As Minchin ('08) points out, however, the 

 developmental history of no trypanosome points to this mode of origin, 

 but tends rather to support the second hypothesis of the origin of 

 trypanosomes from herpetomonas and crithidia-like forms by the 

 posterior migration of the kinetonucleus and blepharoplast, whereby 

 these structures become secondarily posterior, while the flagellum 



FIG. 99 



Trypanosoma noctuse. (After Schaudinn.) Schematic representation of the metamor- 

 phosis of a fertilized cell into an "indifferent" type of Trypanosoma. F, G, H, formation 

 of the undulating membrane and flagellum from kinetoplasmic material. 



would be attached to the cell, as in herpetomonas, at the anterior end. 

 Schaudinn has shown that the flagellum in Trypanosoma noctuce has 

 this mode of origin, and grows out from the anterior end, while the 

 kinetonucleus and blepharoplast (Fig. 99) remain anterior to the 

 nucleus. In other species, however, the developmental history shows 

 that young forms and culture forms are similar to crithidia with 

 rudimentary membrane and anterior blepharoplast and kinetonucleus. 

 This is well described in the case of a trypanosome of the ray, Try- 

 panosome mice (?), by Robertson ('07). Here in young forms, after 

 division in the gut of the leech Pontobdclla muricata, the kinetonucleus 



