W. S. Patton 
101 
we do not see how it is possible to say T. raiae undergoes a true develop¬ 
mental cycle in Pontobdella muricata. Woodcock in criticising Miss 
Robertson’s very cautious remarks regarding the process of conjugation 
of this flagellate boldly says, “it is more probable that conjugation itself 
takes place soon after the transfer of the parasites from one host to the 
other, i.e. after the arrival in the invertebrate; and that the ookinete form 
is the immediate result of the process.” It is difficult to understand 
these wild speculations; such hypotheses, based as they are on erroneous 
conclusions, can hardly help forward this difficult subject. They are 
certainly not suggested by Leger’s work on T. barbatulae, or Prowazek’s 
(1905) work on T. lewisi in the louse. 
Woodcock next shortly describes Keysselitz’s (1906) work on the 
development of Trypanoplasma borreli in Piscicola geometra. According 
to that author, male and female gametes can readily be recognised in the 
blood of the carp, conjugation taking place in the leech and later giving 
rise to the three general types of Schaudinn. We (1909) have else¬ 
where shown that Keysselitz’s developmental cycle cannot be accepted; 
he has not rigidly excluded a natural flagellate from the leech and his 
observations are therefore of little value. From his description we are 
unable to ascertain how Trypanoplasma borreli passes into the develop¬ 
mental forms in the leech. We therefore consider these parasites 
represent part of the life cycle of a Crithidia of the leech ; the fact that 
Keysselitz found that leeches caught at large contained these flagellates 
assuredly suggests this. We would like to know whether any experi¬ 
ments were conducted to exclude a flagellate transmitted hereditarily. 
In a recent paper Miss Robertson (1908) claims to have traced the 
development of a trypanosome of Emyda vittata in a leech. She states 
that the development is similar to what takes place on a slide (sic), and 
which is shortly as follows : “ the trypanosome rolls itself up and the 
flagellum breaks free, but generally still remains attached at the 
kinetonucleus end. The flagellum is motile for a long time, but finally 
comes to rest, lying often in an untidy tangle round the creature. The 
trypanosome divides into two, the daughter individuals generally 
remaining more or less in contact; a further division into two occurs; the 
divisions in every case involve both the tropho- and the kineto-nucleus. 
The result of these divisions is a group of four often very irregular little 
creatures; they become pear-shaped and put out each a flagellum from 
their blunt ends and this gradually lengthens and becomes motile, 
but at first it is quite unable to move the body of this creature. The 
four little flagellates separate and move actively about.” From this 
