118 Viiiversitjj of California Publications in Zoolofji/ | Vol. kj 



(pi. 14, figs. 1-8) and thi.s relation is retained in the subsequent 

 merozoite pha.se resulting from multiple fission (?) (pi. 14. figs. 9-12). 

 In the erithidial form, on the other hand, the parabasal is anterior to 

 the nucleus (pi. 14, figs. 14-18, pi. 15, figs. 20-31). 



The transition appears to result from two processes. The first is 

 a posterior migration of the nucleus (compare figs. 13 and 18), and 

 the second an anterior migration of the parabasal body to a position 

 anterior to the nucleus (figs. 19-23). Quite a variety of pictures are 

 obtainable of this process, so that it is probable that there is no rigid 

 sequence of movements of the organs concerned. 



In addition to the change in position of the two organs named, 

 there is also a structural metamorphosis of each. In this connection 

 we must take the occasion to point out the fact that our conclusion 

 that the trypanosome of the stomach and the erithidial form found 

 therewith are identical species rests merely on similarities to the cycle 

 of Trypanosoma lexvisi, and not as yet upon experimental feeding and 

 infection. While this hypothesis of identity is a reasonable one and 

 proof of it by experiment is to be expected, the ijossibilitij remains 

 of the occurrence here of two specifically distinct organisms. The 

 transition from the cdndition in figures 11 and 12 to that in figure 

 14 or figure 22 is a considerable one, which our material imperfectly 

 bridges. It is more fully bridged in Minchin and Thomson's (1915) 

 account of T. lewisi. 



The metamorphosis of the nucleus is profound. It changes from 

 the elongated, slender, a.symmetrical, granular type ( pi. 14. figs. 9-12) 

 to the spheroidal, symmetrically located, vesicular type I \A. 14, figs. 

 14—19. pi. 15. figs. 20-32 h These two type.s are consistently main- 

 tained throughout the individuals of the trypanosome and erithidial 

 stages respectively, in our material. In both kind and degree the 

 change is not unlike that which Chagas (1909) finds in Schizotry- 

 paniim ertizi in ConorhinKS megistus, but it is considerably greater in 

 both respects than Minchin and Thomson found in T. lewisi in the flea. 



The parabasal also undergoes a metamorphosis in several partic- 

 ulai's. It is (1) more distinct from the blepharoplast, (2) has a more 

 distinct fan-shaped suspensory apparatus, and (3) forms a trans- 

 versely located bar or bilobed structure located, as a rule, inuuedi- 

 ately anterior to the nucleus. 



The process of transition from the trypanosome type to the eri- 

 thidial one is suggested by the anterior progression in location of the 

 parabasal in the early stomach phase (pi. 14, figs. 1-81, and by the 



