WERNER MARCHAND 31 



last body segment and is in no way connected with the intestine, 

 which terminates at the end of the segment before the last, or with 

 the sexual organs. In Graber's account it remains questionable 

 whether the terminal tube, as was supposed, really originates in the 

 integument. The tube and the capsule forming its enlarged terminal 

 part behave histologically like a glandular formation. The main layer 

 is an epithelium consisting of large cells. This is seen best, especially 

 after treatment with 35 per cent potassium hydroxide, at the distal 

 (head) end of the capsule. The cells appear as elongated, sac-like, 

 pale compartments, separated from one another by bridge-like septa, 

 always showing a dark nucleus accompanied by a small nucleolus. 

 In the remaining part no distinct cell borders can be distinguished, 

 but only large granulated nuclei. In the terminal tube the latter are 

 arranged alternating behind one another, similarly as in the narrow 

 secretory ducts of true glands. The epithelial tube is covered at the 

 outside by a thin homogeneous covering which may be considered as 

 a tunica propria. 



The structures belonging to the third stratum, that is, to the 

 chitinous membrane, are peculiar. Leaving aside certain complica- 

 tions, we find first a chitinous capsule corresponding to the epithelial 

 one, which is prolonged into a narrow canal corresponding to the 

 terminal tube. This canal pursues, inside the terminal tube, an un- 

 dulating course, curved alternately to the right and left, suggesting 

 the muscle in the stem of a Vorticella. 



The chitinous capsule enclosed within the epithelial vesicle is 

 often very thin and delicate compared with the thickness of its 

 matrix, and is perfectly transparent. Its free (inner) surface, how- 

 ever, shows at high magnification small tegula-like overlapping 

 scales. In this chitinous capsule the black bodies already mentioned 

 are enclosed. 



At low magnification these bodies appear as simple homogeneous 

 globules. At the highest magnification, however (Plate 9, Fig. 107), 

 they are found to be hollow chitinous structures with a somewhat 

 wrinkled surface, which after the fashion of a volumetric flask are 

 prolonged into a narrow hollow stem or peduncle. The bodies re- 

 main perfectly black and opaque even when boiled in caustic potash ; 

 consequently they seem to have very thick and strong chitinous 



