496 



THE ANATOMY OF IXYERTEBRATED ANIMALS. 



pores on the genital plates, through which their products are 

 extruded. Hoffmann has fcund the peritoneal fluid of the 

 males full of spermatozoa. 



Fig. 145.— Development of an Echinid. (After Muller.)— A, Echinopsedium of Echi- 

 nus pulchellus in the gastrula stage. B, fully-developed Ecbinopaedium (Pluteus) 

 of the same species: a. mouth; b, stomach and intestine; c.anue; A E, processes 

 of the body into which prolongations of the internal skeleton extend. C, the 

 Echinopgeciium of an Echinid in which the Echinoderm is so far advanced that 

 the spines, pedicels, and pedicellariae are visible. D. Echinopaedium of Echinus 

 Rvidus: a, mouth ; a', gullet; b. stomach; b', intestine; c. rudimentary Echino- 

 derm; c', the ambulacral sac; c", the external opening of its duct; A A, EF, B, 

 the processes of the body. 



In the JEchinidea, as in the Ophiuridea, the Echinopae- 



