360 FAMILY: TRYPANOSOMIDyE 



the flagellates represented developmental forms of a cattle trypanosome, 

 but this was considered to be negatived from the fact that only a few 

 ticks from any single animal were found infected. No other ticks on the 

 animals than this particular species showed infection. The cattle, more- 

 over, were invariably healthy. A remarkable feature of the infection is 

 that it is not an intestinal one, but is confined to the body cavity or 

 hsemocoele. At the height of an infection, which occurs just before the 

 tick oviposits, the smallest drop of fluid obtained by cutting off one of 

 the legs is found to be swarming with flagellates. In the early stages 

 of an infection, only round leishmania forms occur, but these gradually 

 develop into the adult crithidia forms. Multiplication takes place in 

 the usual way, all stages of the flagellate participating in this. After ovi- 

 position, and just before the death of the tick, round leishmania forms 

 (post-flagellate forms) may appear in the fluid. The intestinal diver- 

 ticula and Malpighian tubes were not found to harbour the parasite, though 

 as non-flagellate forms they were sometimes found in the salivary glands, 

 but this was exceptional. Infection of the ovaries is described as taking 

 place by the flagellates piercing the walls of the oviducts, and then entering 

 the ova. Some of the flagellates remain in the cells of the oviducts, 

 where they become transformed into leishmania forms. Those that 

 enter the eggs likewise become of the leishmania type, and here they 

 may be seen in process of division. It is unfortunate that, in his account 

 of this developmental process, O'Farrell does not make any reference to 

 the examination of the newly-hatched young. Examination of the ovaries 

 by the section rather than the smear method would have given more 

 trustworthy results as regards the supposed invasion of the eggs. As 

 the author says, the hsemocoele fluid became " a felted mass of crithidial 

 bodies and waving flagella," and it must be difficult in such a case to 

 exclude the contamination of the interior of an egg with hsemocoele fluid 

 when smears are made. 



Several other instances of infection of ova by flagellates are on record, 

 but in all cases the smear method was used, though Porter (19096) claims 

 to have actually observed penetration of the egg of Nepa cinerea by the 

 living flagellate forms of Leptomonas jaculum. Flu (1908), Swingle 

 (1909), and Porter (1910) have described invasion of the ova of Melophagus 

 ovinus, the sheep ked, by the flagellates of these insects. Porter (19096, 

 1909c), though claiming to have observed L. jaculum and C. gerridis 

 within the eggs of their hosts, considers that they degenerate without 

 infecting the egg. This condition is supposed to lead up to that in M. 

 ovinus, where invasion of the ova is said to be followed by multiplication, 

 so that hereditary infection occurs. The statements regarding M. ovinus 

 can hardly be accepted in view of the fact that it is now known that the 



