496 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



pores on the genital plates, through which their products are 

 extruded. Hoflfmann has found the peritoneal fluid of the 

 males full of spermatozoa. 



Fig. 145.— Development of an Echinid. (After Mflller.)— A, Echinopsedium of FcM- 

 mis pulchellus iw the g.istrula sta<re. B, l"ully-deve]o[)ecl Echiuopsediiim {Plutevs) 

 of tlie samo species: a. mouth; J, stomach aiid intestine; c. anus; ^ i^, processes 

 of the hody into which prolonijatlons of the internal skeleton extend. C, the 

 Echinopajfiiiim of an Echinid in which the Rchinoderm is so far advanced that 

 the spines, pedicels, and piHlicellarise are visible. D, Echinopjedium of Echinus 

 lividus: a, mouth ; a', euliet; 6. stomach; 6', intestine; c. rudimentary Echino- 

 derm; c\ the amhulacral sac; c", the external opening of its duct; A A, FF, B, 

 the processes of the body. 



In the Echinidea^ as in the Ophiuridea, the Echinopae- 



