81 
ON THE SUPPOSED DEVELOPMENT OF TRYPANOSOMA 
LEW I SI IN LICE AND FLEAS ; AND THE OCCURRENCE 
OF CRITHIDIA OTENOPHTHALMI IN FLEAS. 
By 0. STRICKLAND, B.A. 
(.From the Quick Laboratory, Cambridge.) 
According to Prowazek (1905) Trypanosoma lewisi undergoes 
sexual development in the rat louse, Haematopinus spinulosus. His 
description of the developmental process may be summarised as 
follows: 
When T. lewisi enters the midgut of the louse, the nucleus under¬ 
goes changes, the chromosomes being reduced from 16 to 4. Then 
some of the trypanosomes become greatly attenuated, the reduced 
nucleus becomes band-like, and the cytoplasm stains differently. The 
attenuated forms are called the male gametes. They are seen to 
copulate with the female gametes by fusion at the non-flagellate end. 
The resulting zygote then develops into a trypanosome by the formation 
of a new kinetonucleus and locomotor apparatus. 
Swingle (1907, p. 117), who examined fleas taken from rats harbouring 
T. lewisi, believed that he had observed a similar development to that 
described by Prowazek in the louse. He however did not describe any 
conjugation. 
Woodcock (1909, pp. 196—273), who has lately reviewed the subject, 
believes that it has been “ reasonably proved ” that T. lewisi, like other 
trypanosomes, has a true alternative host. Although he has not ap¬ 
parently studied the subject at first hand, he concludes that the flea is 
the true alternative host of T. lewisi. 
On the other hand MacNeal (1904, p. 520), working in America, 
could never trace any developmental changes of T. lewisi in lice (species ?), 
nor could Captain Patton, working in India, find any development of 
T. lewisi such as Prowazek has described in lice. 
Parasitology n 
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