SYNAPTA VIVIPARA. 



85 



11. EXPLANATION OF PLATES. 



[AH figures except 20 and 23 were drawn with the aid of a camera lucida.] 

 ABBREVIATIONS USED. 



A. atrium. 



AE. anterior euterocoel. 

 AN. anus. 

 AO. atrial opening. 

 AT. accessory tentacle. 

 BC body-cavity. 

 BL. blastopore. 

 BV. blood-vessel. 

 CF. ciliated funnels. 



CH. cireumoesophageal ring of blood-system. 

 CM. circular muscles of body-wall. 

 CR. calcareous ring. 

 CT. connective tissue. 

 Car.R. cartilaginous ring. 



Cir.S. circular sinus formed from the anterior-prolon- 

 gation of the left coelom. 

 DV. dorsal vein of blood-system. 

 E. enterocoel. 

 Ect. ectoderm. 

 Epi. epithelium. 

 Ey. eyes. 

 GD. genital duct. 

 GG. genital gland. 

 H. hydrocoel. 

 I. intestine. 

 LC. left coeloin. 



LGO. larval glandular organ. 



LM. longitudinal muscles. 



M. mouth. 



Mes. mesenchyme. 



MD. madrepore. 



MY. mesentery. 



NR. circumoral nerve-ring. 



O. otocysts. 



OE. oesophagus. 



OEN. nerve-band to mouth and oesophagus. 



PT. primary tentacle. 



PV. Polian vesicle. 



R. rectum. 



RC. right coelom. 



RN. radial nerve. 



SC. stone-canal. 



SO. secondary outgrowth of the hydrocoel. 



SP. sense-papilla. 



T. tentacle. 



TC. canal of tentacle. 



TN. tentacle-nerve. 



TV. blood-vessel on inner side of tentacular canal. 



V. valves. 



WP. . water-pore. 



WR. water-ring. 



