CRITHIDIA HYALOMM/E 361 



flagellate, which was supposed to be peculiar to the ked, is the develop- 

 mental form of the sheep trypanosome. Hoare (1921a), working in the 

 writer's laboratory, could find no evidence of invasion of the eggs of either 

 M. ovinus or N. cinerea, but noted the accumulation around the ova 

 of spermatozoa, which produced an appearance of discarded flagella. 

 It is possible that these were mistaken for the flagella of flagellates. 



Prowazek (19126) described infection of the egg of Sarcophaga by 

 L. sarcophagce, but it is not clear that intestinal contamination was 

 avoided. It is evident the question of transmission of flagellates through 

 the ova requires to be studied by the more accurate method of sectioning 

 the ovaries and eggs. In the case of such a host as Hyalomma cegyptium, 

 which, apparently, only sucks blood, it would appear that ovarian infec- 

 tion would be the only method of transference from host to host if the 

 possibility of a cattle trypanosome is excluded. In this connection it must 

 not be forgotten that the apparently harmless Trypanosoma theileri is 

 often present in cattle in such small numbers that it can only be demon- 

 strated by culture methods. This source of the infection in the tick has 

 not been considered, nor is mention made of any infection in the newl}'- 

 hatched nymphs. Only ticks which had been feeding on the cattle were 

 found infected. It is evident that the infection of the eggs, and the supposed 

 hereditary infection of offspring hatching from the eggs, has not been demon- 

 strated for C. hyalommcB nor any of the other flagellates mentioned above. 



Crithidia euryophthalmi McCulloch, 1917.— This flagellate is parasitic 

 in the gut of the bug Euryophthahnus convivus, which feeds on the plant 

 Lupinus arboreus, growing in sand dunes near San Francisco (Fig. 168). 

 It was discovered by McCulloch (1917), who has given an account of its 

 life history, which is of interest in that two phases of development not 

 hitherto recorded in the life-history of these flagellates are described. 

 These are multiple segmentation and internal budding. The alimentary 

 tract of the bug consists of fore-, mid-, and hind-gut (Fig. 168). The 

 fore-gut is made up of the mouth, pharynx, oesophagus, and proven- 

 triculus; the mid-gut of the crop, mid-stomach, pyloric expansion, and 

 intestine; and the hind-gut of the colon, into which open the Malpighian 

 tubes and the rectum. The type of flagellate found varies with 

 the position in the gut. The oesophagus and proventriculus have 

 always been found free from infection, the hind-gut has shown a 

 slight infection in the rectum in some instances, while it was in the 

 mid-gut that the heavy infections occurred. The stages which usually 

 occur in the hindgut of insects are in this bug found in the pyloric 

 expansion. 



The forms which occur in the stomach (crop, mid-stomach, and pyloric 

 expansion) are: 



