TURBELLARIA. 185 
respiratory or circulatory organs, the body cavity is not 
represented, unless it be by intercellular lacune in the 
parenthyma; the excretory system usually consists of two 
longitudinal canals, whose branches end internally tn flame- 
cells. The Turbellarians are almost always hermaphrodite ; 
and the reproductive organs usually show some division of 
Fic. 94.—Diagram of Turbellarian.—After Lang. 
C., Cerebral ganglia; £., eye; 7., tentacle; PH., pharynx; MJo., mouth; 
M., male aperture; /., female aperture; the ovaries and testes are 
branched organs on both sides, represented by dots. 
labour, e.g. in the development of a yolk gland, which may 
have arisen as an over-nourished (hypertrophied) part of the 
ovary. The eggs are usually enclosed in shells or cocoons, 
and the development may include a metamorphosis. Some 
forms multiply by fission. There seem to be affinities between 
Turbellaria and Calentera, especially the Ctenophora. 
