SPIROCHAETES 



25 



similar to the chromatin granules found in ordinary cell nuclei.* 

 The organisms are about 5[a thick and vary in length from 20(V 

 to S00\i. 



Fig. 13— CRISTISPIRA 

 BALBIANII 



A large spirochaete from the diges- 

 tive tract of an oyster. The "crista," 

 or winding flange-like shelf, is not 

 an undulating membrane but is rigid. 



From a photomicrograph by the author 

 Magnification, 1000 



Another free-living but much larger type, Saprospira (Fig. 

 12), is also found in polluted waters. It is several times thicker 

 than spirochaeta and resembles certain types of algae except for 

 the absence of chlorophyll. t Reproduction of this form is 

 normally by transverse division, but it also reproduces by the 

 formation of so-called "coccoid bodies" which are analogous to 

 the spores of bacteria. Like the latter, saprospira is made up 

 of an aggregation of the internal chromatoid granules. There 

 is no columella, and no differentiations of any kind are apparent. 



Another type of spirochaete, Cristispira (Fig. 13), differs 

 from the two types described above, in having a definite spirally- 

 wound flange-like shelf running the length of the body. These 

 forms are never injurious to man; they are present as parasites 

 in practically all oysters and clams, but they do not cause any 

 apparent harm. The several species of this genus, as well as 

 all species of the next genus, Treponema, are parasitic forms — 

 some harmless and some pathogenic. Cristispira was discovered 

 in 1882 by A. Certes in one of the organs of the oyster in which 

 it lives. Practically every oyster, if examined immediately after 

 removal from the water, can be found to harbor this spirochaete. 

 It is smaller than Saprospira and differs from Spirochaeta in 



* See "Heredity and Variation," page 44, in this Scries. 

 t See "The Plant World," page 13, in this Scries. 



