2 University of California Publications in Zoologij [Vol. 16 



paper in eonneetiou with a discussiou of the group, ncrpetomonas, 

 Crithidia, and Trypanosoma. 



The type is in the protozoological collections of the Zoological 

 Laboratory of the University of California and a cotype has been 

 deposited in the United States National Museum at Washington. 



2. Importance 

 The importance of such a study is clear when it is taken into con- 

 sideration that a thorough investigation of the life-cycle of Crithidia 

 will be essential in order to explain the complete life-cycle of Try- 

 panosoma. The material of Crithidia leptocoridis is invaluable for 

 such a study. In the first place, the box-elder bugs can be obtained 

 readily throughout the year and the mature insects show a hundred 

 per cent infection; secondly, multiple fission forms of this parasite, 

 which may be intracellular, have been found here, indicating that 

 the life-cj-cle of Crithidia leptocoridis is very similar to that of Try- 

 panosoma lewisi recently described by Minchin and Thomson (1915) ; 

 thirdly, the crithidial stages of Schizotrypannm cruzi as figured by 

 Chagas (1900) are almost identical with certain stages in the life- 

 cycle of Crithidia leptocoridis. 



3. IMethods 



The material used in this investigation includes the living material, 

 stained smears and sections, cross and longitudinal, of the entire bug 

 and of the digestive tract. 



For the study of the living material, the intestinal tract was 

 removed in one of two ways. For ordinary work the tip of the abdo- 

 men was clipped off, the contents pushed out with a needle upon a 

 slide and covered with a drop of Ringer's or normal salt solution. 

 For more careful work the digestive tract was dissected out in 

 Ringer's solution and then transferred to a slide. By pressing down 

 the cover slip firmly and examining under a microscope, the parasites 

 could be seen in situ through the intestinal wall. 



In determining the localization of the parasites, the digestive tract 

 was cut carefully into its several parts, the stomach, mid-intestine, 

 ilium, colon, and rectum. Each part was then teased out with needles 

 and mounted under a cover glass. Such preparations were frequently 

 sealed with vaseline and studied for a period of five or six days. More 

 permanent cultures were prepared by making a hanging-drop culture 



