276 H. M. WOODCOCK. 



ably be inferred that^ iu the latter forms alsOj the result is 

 attained in the same manner^ by the passage backwards of 

 the kiuetonucleus from the flagellate (anterior) end; and that 

 iu the other species of Trypauosoma, in which the kiueto- 

 nucleus is practically terminal, this body has merely passed 

 still further back, right to the non-flagellate (posterior) 

 end/ thus bringing about the great development of the 

 undulating membrane. 



This is, in fact, the explanation given by the adherents of 

 the Herpetomonadine theory. They consider that the con- 

 dition observed in young parasites of T. lewisi, formed by 

 ''budding" or multiple division (see above, p. 238 et seq., 

 and, figs. 27 — 29), furnishes strong support to this view; 

 and, indeed, they look upon the manner in which the young 

 forms become adult in this parasite as indicating the actual 

 course of morphological evolution in Trypanosoma. Did 

 these facts constitute the only evidence available, there could 

 be, it is needless to say, little doubt as to the correctness of 

 the monophyletic theory. When, however, we bear iu mind 

 the many opposing facts already discussed, including certain 

 biological considerations of fundamental importance which it 

 is difficult, if not impossible, to reconcile with this view, we 

 are bound to conclude that the migration of the kiueto- 

 nucleus cannot possess the significance attributed to it. 



There is one point which may be suggested as perhaps 

 accounting, at any rate in part, for this feature. It may be 

 regarded as proved beyond question that the kiuetonucleus 

 is of nuclear origin. Hence its wandering propensity in 

 general and frequent contiguity to the trophonucleus are not 

 difficult to understand. This association of the two organella 

 is particularly marked in cases of multiple division, Avhether 

 occurring in normal (figs. 27, 28) or in cultural conditions 



' Admitting, for the moment, that this explanation of the position of the 

 kinetonucleus in Trypanosoma is possihle, it must be emphasized that the 

 argument relative to the other morphological characters is not thereby 

 invalidated; for no intermediate stages in the " reversal" of their position 

 ar« known (of. H. subulata, and especially Trypanomorpha). 



