516 C. CLIFFORD DOBELL. 



might therefore display any breadth between 1 fx and 1'6 jx. 

 It' the breadth of C. veneris is therefore a little more than 

 1 n — that is, about 1*2 /u, subject of course to slight individual 

 variation — then the different breadths observed in stained 

 specimens are easily accounted for by the different degrees of 

 flattening Avhich different individuals have undergone in the 

 process of making the preparations. I believe, therefore, that 

 the body of C. veneris is cylindrical, and has an actual 

 uniform diameter of approximately 1"2 fx in the living 

 organism. 



I have already described a similar apparent variation in 

 bi'eadth — due, I believe, to the same causes — in the case of 

 Bacteria (see Dobell, 1910a). The apparent variability in 

 the breadth of different individuals of Cristispira is a point 

 of some importance when considered in relation to the method 

 of division (see p. 52G). 



As in other members of the genus, the body of C. veneris 

 possesses a spiral, corkscrew-like shape. The number of 

 complete turns in a full-grown individual is approximately 

 four. The number is greater than this in dividing indi- 

 viduals (five or six), and less in newly divided individuals 

 (two or three). 



In the living organisms, I have not been able to distinguish 

 any structure in the protoplasm of the cell, which appears 

 homogeneous under the highest magnification which I was 

 able to employ (Leitz yV in. oil-immersion x ocular 5, using 

 direct sunlight for illumination). A few small retractile 

 granular inclusions were usually to be seen in the proto- 

 plasm. 



The ends of the organism are bluntly pointed (see fig. 1, 

 PI. 20), being less rounded than the ends of C. balbianii 

 and less pointed than those of C. an o don t a-. The body 

 usually tapers very slightly towards the two ends. The 

 structures called *' polar caps," described in C. balbianii, 

 C. pectinis, etc., are not observable in C. veneris. They 

 appear to be confined to the species which possess rounded 

 ends. 



