56 



PHYLUM TUXICATA (UROCHORDA). 



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

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



' at I 



SO 



si 



ov 



FIG. 47. Doliolum denticulatiim, sexual form, from the left side (after Herdmau). at at rial 

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

 end endostyle ; h heart : i intestine ; >;' m* muscular rings ; n nerve ; ng ganglion ; ov ovary ; 

 pbr atrial cavity; pp peripharyng"al liand ; g 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, 



Flo. 48. Old larva of Duliolinn i-/ifi-ni>r,;/i, ;itt.-r I'ljanin, from Korschelt and Heider). ch 

 notochord ; d dorsal appendage ; ' endnstyle ; h heart and pericardium ; m vitelline mem- 

 brane ; n ganglion ; r rudiment "I -tnlmi in^cttc-shaped organ). 



