THE GENERA HERPETOMONAS AND CRITHIDIA 



241 



Patton finds no evidence of encystment and no evidence of infection 

 of the bedbugs other than from human victims. Nor is there any 

 evidence to support the idea of (Hrect inheritance from female bugs to 

 their offspring, but Patton suggests in a later paper (1908) that nymphs 

 of blood-sucking forms of such bugs may take in the infection with 

 their food. The method of reentry into a human host is likewise 

 unknown. 



B. The Genus Crithidia, Leger, 1902. — The genus crithidia, by 

 reason of its non-kinetic prolongation of protoplasm at the base of the 

 flagellum, forms an interesting link in the evolution of the trypano- 

 somes. It is quite true, as Novy, MacNeal, and Torrey ('07) point 

 out, that the distinctions between these several genera are extremely 

 "fragile," and that the points of difference are so minute as not to 



Fig. 95 



Crithidia melopliagia. Flu, from tlie gut of .Melophagus ovinus. (After Flu.) A. fully 

 developed para-site with myoneines; B, individual with degenerated trophonucleus; C, 

 encysted form (see herpetomona.") ; D, divir^ion form. 



cf)uiit for much. It must not be overlooked, however, that minute 

 (iitlVrences must be utilized in connection with organisms that are 

 themselves minute, and a definite structural feature whicii Liihe 

 j)oints out as the most characteristic of the genus crithidia, since it 

 exists in all of the parasites regardless of their size, is a perfectly 

 .satisfactory differential characteristic, and unlike Leger's original 

 basis of distinction (smaller size of crithidia and truncated eiulsj, 

 has morphohjgical value. 



The type species is Criihldld .siihulata, Leger, a parasite of the 



intestinal tract of a tabanid fiy. The body is elongate and slender and 



drawn out iij)on the base of the Hagelluin in a tyj)ical inaniuM- ( l''ig. WA, 



J). 2)^.")). Tlie nucleus and blepharoplast are distinct and persistent after 



1(1 



