﻿Tryimnosome found in Pontobdella. 



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cases such as Fig. 58, where the one product of division is 

 a broad, short individual much richer in protoplasm than 

 the other. These specimens, when seen alive, are most 

 extraordinarily suggestive of the conjugation of a 

 male and female gamete, and many hours were spent 

 in observing these creatures in the live state in the hope 

 of seeing them fuse completely together. This, however, 

 never happened, and the study of the stained specimens 

 finally settled the question most convincingly in favour of 

 division. 



I have drawn attention to these points because one feels 

 that conjugation among the Protozoa is such an interesting 

 and important question, and at the same time of such great 

 difficulty, that more especial care must be exercised lest 

 faults in observation confuse a phenomenon whose meaning 

 is already sufficiently obscure. 



It is impossible not to observe that the tendency of 

 modern protozoan research is to interpret appearances as 

 conjugation upon rather slender evidence, and this criticism 

 is, perhaps, more particularly applicable to the literature 

 dealing with the typical trypanosomes. On the other hand, 

 one is led to expect, from theoretical consideration, that 

 this process must take place at some point of the life- 

 cycle. 



I should like to record in passing that a Hsemogregarine, 

 closely resembling Hcemogregarina delagei, Lav. and Mesn., 

 parasitic in the red corpuscles of the skate, has occasionally 

 been met with in the intestine of the leech. The life-cycle 

 of this form has not as yet been traced. 



The work here recorded was done in the Zoological 

 Laboratory of the University of Glasgow under the direction 

 of Professor J. Graham Kerr, whom I have to thank for 

 many kind suggestions and much valuable advice. 



My thanks are due to the Carnegie Trust for pro- 

 viding me with additional microscopical apparatus, which 

 was of great assistance in carrying out the research, 

 and, further, for defraying the expense of the necessary 

 illustrations. 



