218 ANN1J5 POUTER. 



of the solution so obtained was made much brighter when an 

 emulsion of crushed salivary glands of the ked was added to 

 it. The leucocytes of the sheep's blood occurring in the gut 

 of the ked do not appear to be affected in any way by the 

 anti-coagulin. 



Anti-coagulin appears to be found in all parts of the alimen- 

 tary canal of the ked and to decrease in amount from before 

 backwards. As before mentioned, I determined experi- 

 mentally that freshly shed, and therefore fluid, blood acted 

 as a stimulant to division of the Crithidia. This artificial 

 condition is the counterpart of the natural condition of the 

 blood within the fore-gut of the ked. There, owing to the 

 action of the anti-coagulin, the freshly ingested sheep's 

 blood does not clot, but remains fluid. It is probable that 

 Crithidia within the gut are stimulated by this fluid blood, 

 and divide rapidly. I obtained similar results in the case of 

 Herpetomonas jaculum, where "division of the flagellate 

 Herpetomonad takes place rapidly under natural conditions 

 after ingestion of blood by the host" (Porter [1909], p. 382). 

 If the Criti/idia are in the pre-flagellate condition the rapid 

 multiplication is followed by the outgrowth of flagella, after 

 which the organisms separate and pass further down the 

 alimentary canal. The presence of anti-coagulin, from the 

 salivary glands, in the contents of the fore-gut of the ked 

 may be the cause of the rapidity with which the pre-flagellate 

 stage of Crithidia melophagia is passed through, the 

 blood, kept fluid by the anti-coagulin, acting as a stimulus 

 to further development. 



References to Liteijature. 



Further references will be found at the ends of some of the papers 

 quoted. 



Bruce. Sir David. Hamerton. A. E., Bateman. H. R., and Mackie. F. P. 

 (x. 1909). — "The Development of Trypanosoma gambiense 

 in Glossina palpalis," • Proo. Roy. Soc./ ser. B. Ixxxi. 

 p]j. -iOo-iU. pis. 10, 11. 



