8o SOME MINUTE ANIMAL PARASITES 



attach themselves to the corpuscles floating in the 

 fluid, or may even penetrate them and live within 

 them. Whether they remain in the gut or not, the 

 spirochaetes sooner or later begin to divide to pro- 

 duce small spores exactly in the same way that has 

 been described for those present in the blood of the 

 vertebrate. The concentration of the protoplasm 

 around the chromatin bars and the concentration of 

 the outer portions to form the coats of the spores, 

 occur, perhaps, at a somewhat quicker rate than 

 they do in the blood, while the periplast sheaths are 

 more rapidly disintegrated. But the procedure is 

 not really varied in any way ; the rate of spore forma- 

 tion alone is affected. 



Mention has been made of the fact that the 

 spirochaetes are capable of leaving the gut and of 

 entering the body fluid. Some of the spirochaetes 

 penetrate the haemocoelic corpuscles, and there 

 divide rapidly to produce ovoid bodies or spores. 

 Other spirochaetes divide while still free in the 

 haemoccelic fluid, and the small, ovoid bodies pro- 

 duced are carried to the various organs. Some find 

 their way from the gut into the Malpighian tubules 

 and form granules. These are voided with the excre- 

 tion, and thus may enter any host bitten by the tick. 



The Malpighian secretion is not the only means 

 by which infection is spread. The full-grown spiro- 

 chaetes and the ovoid, coccoid bodies alike are carried 

 in the haemocoelic fluid to the ovaries, and penetrate 

 the ova. The development of the spirochaetes in the 

 egg was first demonstrated by Leishman, and was 

 confirmed and amplified by Balfour, Fantham, 



