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THE AMERICAN NATURALIST [Vol. XLII 



intermediate host (Argas). Very recently Balfour 

 (1907) has seen the spirochete actually enter the red 

 corpuscle, and undergo changes within it in which the 

 chromatin core is broken up into separate globules. This 

 stage is very difficult to stain and has hitherto escaped 

 emphasis. Some observers believe it to represent degen- 

 eration changes; even then it is incompatible with the 

 theory of bacterial relationship, while, on the other hand, 

 it suggests strongly conditions which prevail among other 

 hematozoa. One is forced to note its great resemblance 

 to the "latent body" of trypanosomes recently described 

 by Moore and Rreinl. This consists of a nucleated frag- 

 ment of protoplasm which is stored up in spleen and 

 bone marrow of infected animals and ultimately reap- 

 pears in the circulation when it gives rise to a new 

 trypanosome. 



Jaffe (1907) has studied a form (*S. culicis) found in 

 mosquito larvae and gives a careful analysis of the motile 

 phases which stand in sharp contrast with the stiff screw 

 movements of spirilla. He emphasizes also the ribbon- 

 shaped body, the great susceptibility to solution of KOH 

 even though very dilute, the axial nuclear ( ?) thread, and 

 the occurrence of both transverse and longitudinal divi- 

 sion. 



The last work by Dutton and Todd (1907) demon- 

 strated for S. duttoni a ribbon-shaped body with a cen- 

 tral deeply staining core and a lighter periplastic sheath 

 which at one end at least is prolonged into a flagellum. 

 The central core does not stain uniformly, but has un- 

 stained areas and is sometimes broken up into granules. 

 While these organisms occur singly, chains of three or 

 four are frequent. They usually multiply by transverse 

 fission, but longitudinal division also occurs periodically. 

 Many forms taken from spleen and bone marrow are 

 tightly coiled and a few of these undergo remarkable 

 changes there. Tn the tick involution changes were ob- 



process takes place in tbo Malpigh'mn tubules where ap- 



