56 



PHYLUM TUNIC ATA (UROCHORDA). 



and the testis ripens. The egg surrounded by its layer of follicle 

 cells passes into the cloaca and thence into the sea. After 



jbr 



ai 



J>rl\ 



so" 



FiQ. r 47. Doliolum denticulatum, sexual form, from the left side (after Herdman). at atrial 

 aperture ; at.l atrial lobes ; br mouth ; br.l buccal lobes ; brs pharynx ; dt dorsal tubercle ; 

 end endostyle ; h heart ; i intestine ; w 1 m% muscular rings ; n nerve ; ng ganglion ; ov ovary ; 

 pbr atrial cavity; pp peripharyngeal band ; sg stigmata ; sgl subneural gland ; so sense organs ; 

 st stomach ; tes testis. 



fertilisation it secretes a vitelline membrane and falls to the 

 bottom. Here it develops into a tailed larva by a process, of 

 which all the stages have not been followed. It begins to swim 

 by means of its tail while still within the vitelline membrane, 



FIG. 48. Old larva of Doliolum ehrenbergii (after Uljanin, from Korschelt and Heider). ch 

 notochord ; d dorsal appendage ; e endostyle ; h heart and pericardium ; m vitelline mem- 

 brane ; n ganglion ; r rudiment of stolon (rosette-shaped organ). 



