5 . THE PHYLUM PROTOZOA
185
Description. Body more or less conical, with rounded anterior
tapering end, 27-169 p long (average 81.2 p ) x 20-34 p wide (average
27.8 p) ; cytostome a t posterior end ; peristome spirals posteriorly ;
cilia of approximately same length except for peristomal long trailing
cilia; definite aciliate girdle between anterior portion of body and
peristomal area; macronucleus oval, in anterior half of body; micro-cv
- cv
FIGS. 89-91. Thigmotrichous ciliates. (89) A ncistrum japonica (redrawn after Uyemura,
1937) ; (90) Boweriu subcylindrica, left view; (91) B. subcylindrica, ventral view
(redrawn after Issel, 1903). CV, Contractile vacuole; F V , food vacuole; M N ,
macronurleus ; N , micronucleus.
nucleus, 3.5-4.5 p in diameter, anterior to macronucleus ; contractile
vacuole near posterior margin of body ; cytoplasmic “ corpuscles ”
scattered throughout ; food vacuoles limited to posterior half of body.
Other information. According to Issel, this ciliate is sedentary on
its host’s gills with its cytostome held against the host’s tissues. This
is suggestive that it may be a true parasite feeding from the apposed
tissues although some consider it to be a commensal.