686 THE INVERTEBRATA 



All that is left of the walls of the branchial chamber (Fig. 482) is 

 the endostyle and a dorsal (hyperpharyngeal) bar, known as the 

 "gill", which runs in a slanting direction along an immense internal 

 cavity formed by the confluence of the branchial and atrial chambers 

 through the absence of lateral branchial walls. The animal is as 

 transparent as glass, save for a small, coloured "nucleus" where the 

 stomach and intestine are situated. 



Salpa (Figs. 478, 481). The chain of blastozooids is band-like. 



Cyclosalpa, The chain of blastozooids forms rings. 



Order DOLIOLIDA (CYCLOMYARIA) 



Thaliacea which have a tailed larval stage; whose oozooid is well 

 formed and free; whose pharynx has several stigmata on each side; 

 and whose blastozooids break free one by one from the stolon as buds 

 which subsequently make attachment to a dorsal process (cadophore) 

 of the parent, by whom they are carried for some time. 



The larva has the barrel-shaped body of the adult with a tail at- 

 tached ventrally at the hinder end: it lies free in its test. Dorsally 

 behind it has already the rudiment of the cadophore. In the adult 

 oozooid the cadophore elongates, as the buds, wandering round the 

 body from the ventral stolon, begin to settle down and develop. The 

 bodies which break off from the stolon are known as probuds. They 

 travel by the pseudopodial activity of certain of their ectoderm cells, 

 and on arriving upon the cadophore divide several times to form the 

 definitive buds. These fasten themselves in a lateral and a median 

 row on each side. Eventually they grow into individuals of three 

 kinds, which co-operate in a remarkable manner. Those of the lateral 

 row become gasterozooids which gather food for the community, 

 those of the median row phorozooids which act as nurses, and others 

 gonozooids carried by the phorozooids. The latter presently break free 

 with their charges, which are ultimately liberated to reproduce 

 sexually. 



Doliolum (Fig. 483). 



