TURBELLARIA. 



181 



respiratory or circulatory organs ; the body cavity is not 

 represented^ unless it be by intercellular lacuna in the 

 parenchyma ; the excretory system usually consists of two 

 longitudinal canals, whose branches end internally in flame- 

 cells. The Turbellarians are almost always hermaphrodite ; 

 and the reproductive organs usually show some division of 



ffl- 



FIG. 94. Diagram of Turbellarian. After Lang. 



C. t Cerebral ganglia; 2?., eye; T., tentacle; PH., pharynx; Mo., mouth; 

 M.) male aperture; F., 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 (hypertrophierf) 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 Cozlentera, especially the Ctenophora. 



