ANNULOSA. 



37 



B 



Fig. 30. Tsenioidea. A, Tcenia sollum, of the natural size : o, "Head" or "nurse;" 

 b, One of the proglottides from the sexually mature part of the worm. B, A single mature 

 proglottis of the same, showing the genital pore (p) and the branched uterus (M). 



ORDER II. TREMATODA. 



Sub-ord. 1. Distomata (Digenea). Monostomum, Diplo- 

 stoma, Distoma (fig. 31), Gyncecophorus. 



Sub-ord. 2. Polystomata (Monogenea). Polystomum, Tris- 

 toma, Diplozoon, Gyrodactylus. 



Myzostoma is a singular little organism, found living as a parasite upon 

 Comatula and other Crinoids, and showing many points of affinity to the 



