12 



PLANT-ANIMALS 



[CH. 



at any point of the body, generally, however, toward 

 the hinder end. 



Neither species of Con voluta possesses a circulatory 

 system. In the absence of heart and blood-vessels, the 

 distribution of the nutritive substances derived from 

 the food is effected in a primitive manner, the materials 

 being passed from cell to cell. 



Fig. 4. Convoluta paradoxa. a. Seen from ventral surface, showing 

 the folds of the sides of the body. b. An animal with nearly 

 ripe eggs (E). 



There is, moreover, no excretory apparatus, and 

 the waste products are not discharged from the body 

 but remain and accumulate in the tissues. 



Both C. roscoffensis and C. paradoxa are herma- 

 phrodite, each animal possessing male and female 

 reproductive organs, the essentials of which are, re- 

 spectively, spermatozoa and egg-cells. The eggs are 

 numerous and attain to so considerable a size that 



