422 



ZOOLOGY 



SP:<T 



modified by the formation, except in the Crinoidea, of variously 

 arranged processes along its course. The resulting larva, echino- 

 'pcediuni or dipleurula, always exhibits marked bilateral symmetry. 

 It has a pre-oral lobe on which an apical plate comparable to that 

 of the trochophore (p. 316) may be developed. 



Fui. 348. Diagrams ot the development oi thr larva' of Echinodcrms.. 1 . I'mmtno torni 

 of Echinoderm larva; 2 and 3, Development of :in ivirii-ulnrin ( flolotlnm>idr;i) ; 1. ">, aiul '.. 

 Development of a bipinnariti (Astn-oidca) ; 7. S. and '.'. Di'xeliPiimcnt of a i>lut<'i<* (Echi- 

 noiclea and Ophiuroidea). aor. in I and 7, adornl l>ancl \ ( -ili:i, in 4, 5 and <i. pir-oral loop ; 

 all. alimentary canal : an. anus ; b, b. proecs-rs \ -,\\\\\+ ; I/H>. mouth ; per. in 1, ^. 7 ami i'. 

 peri-oral ciliated baud and processes, in :i, 1, r> and i>, post -oral loop. (From Leuckart and 

 Nitsche's Diagrams.) 



