90 



BRITISH FRKSHWATER RHIZOPODA. 



the plane of the aperture makes with the longitudinal 

 axis of the test is normally small but is subject to 

 considerable variation, and tests sometimes occur in 

 which this angle may attain to 70 or 80; the aperture 

 is then nearly terminal. The amount of compres- 

 sion of the test varies ; normally a transverse section 



FIG. 151. Portions of tests of Trinema enchelys with different types 

 of scales, x 1000. 



through the widest part is sub-circular, but a ventral 

 compression of 25 per cent, is not uncommon, and 

 occasionally tests with a lateral compression occur. 



There is but little variation in the character of the 

 plasma, which contains few inclusions ; the pseudopodia 



FIG. 152. Trinema enchelys. a, scales in section ; b, c, different types 

 of aperture ; d, aperture in side view, x 1000. 



usually number three or four but may be twice or 

 three times as many and may attain a length equal to 

 twice that of the test. Conjugating individuals are 

 not infrequent. 



The comparatively large circular plates of which 

 the test is composed distinguish this species from 

 Corythion dubium or any form of Difflugia constricta. 



