ZOOLOGY 



larvae. When it has caught a Daphnia, for instance, it will 

 wrap its body round it and attack it with its proboscis ; very 

 frequently it makes prisoners of its prey by ensnaring them 

 with threads of mucus. In the autumn these animals become 

 of an opaque white colour, lose their power of movement, and 

 sink to the ground. The survival of the species through the 

 cold of winter is ensured by the existence of the well- 

 protected winter eggs, a device frequently met vnth amongst 

 fresh-water creatures. 



Mesostoma is not a large Turbellarian ; the marine forms 

 often measure more than an inch in length, and are usually 

 flattened and leaf-like (Fig. 55); the land Planarians, on the 



Fia. 61. — Plan of an Aooelous Turbellarian. 

 After Von Graff. 



1. Eye. 



2. Mouth. 



3. Otolith. 



4. Ovary. 



5. Digestive parenchyma. 

 8. Testicular follicles. 



7. Vesicula semlnalis. 

 (J. Male copulatory organ. 

 (J 5 . Common sexual aperture. 



other hand, are elongated and linear : one of this has been 

 described which attains a length of nine inches. The marine 

 forms are often brilliantly coloured, and their dorsal surface 

 beset with papillae. 



