33 
upon an infection of certain African bugs with a Herpetomonas, says (10) 
expressly that while the herpetomonad (or leptomonad) forms of the 
parasite were met with unaccompanied by crithidial forms, the con- 
verse was never observed. I think it is quite likely that many Cri- 
thidiae may shew a semi-leptomonad phase, just as the crithidial forms 
of a Trypanosome may pass into such, either in cultures, or in the 
Invertebrate host; but that either the one or the other has a true lepto- 
monad phase, comparable to that of a Leptomonas, seems to me to 
be doubtful; at any rate such a phase remains to be described. Pro- 
visionally, therefore, a Crethidia may be characterized as a form which 
possesses the typical crithidial features, enumerated above, which has 
not developed a trypaniform phase and which in most cases no longer 
possesses a typical leptomonad phase. 
The relationships of the different generic types above discussed to 
one another are best indicated, it appears to me, not by representing 
the different forms im one phylogenetic line or series (thus, Leptomo- 
nas — Herpetomonas — Crithidia — Trypanosoma, or Leptomonas — 
Crithidia > Herpetomonas > Trypanosoma), but rather as comprising 
two distinct branches from a Leptomonad stock. For one can hardly 
suppose Crithidia to be derived from Herpetomonas by the loss of the 
herpetotrypaniform phase, only to give rise to Trypanosoma by the re- 
development of a similar phase again; and on the other hand, it is not 
likely that Herpetomonas with its well-marked, persistent leptomonad 
phase, has been developed through Crithidia. Herpetomonas most prob- 
ably represents one branch or line of development from Leptomonas, 
Crithidia and Trypanosoma together, another. The idea may be expres- 
sed diagrammatically as in the accompanying text-figure 1. 
References. 
C. R. soc. biol. 54. 1902. p. 354. text-figs. 
J. inf. diseases. 4. 1907. p. 223. 7 pls. 
Arch. Protistenk. 12. 1908. p. 131. pl. 9. 
Arch. Protistenk. 15. 1909. p. 333. pl. 30. 
Q. J. micr. sci. 56. 1911. p. 645. pl. 31. 
Arch. Protistenk. 31. 1913. p. 1. 3 pls. 
C. R. soc. biol. 71. 1911. p. 578. 
Q. J. micr. sci. 55. 1910. p. 641. 5 pls. 
Sci. Mem. med. Ind. No. 57. 1912. 21 pp. 1 pl. 
Proc. Roy. Soc. 85. 1912. p. 234. text-figs. 
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© © D 1 © OUR ww 
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3. Einige kritische Bemerkungen zu neueren Mitteilungen über Trichoplax. 
Von Franz Eilhard Schulze. 
eingeg. 6. Januar 1914. 
Das im Erscheinen begriffene vortreffliche »Handwörterbuch der 
Naturwissenschaften«, welches zweifellos auf Jahre hinaus über den 
Zoolog. Anzeiger. Bd. XLIV. 3 
