THALIACEA 607 



Order PYROSOMATIDA (LUCIAE) 



Thaliacea which have no larval stage; whose oozooid is degenerate 

 and retained within the parent; whose stolon contains a single epi- 

 cardial tube ; and whose blastozooids at first form a short chain, but 

 subsequently by budding constitute a cylindrical colony of ascidian- 

 like individuals. 



Pyrosoma (Fig. 454). The only genus. The colonies vary in length 

 from an inch or two to several feet, and are phosphorescent, from 

 which fact the generic name is derived. 



Order SALPIDA (HEMIMYARIA) 



Thaliacea which have no larval stage ; whose oozooid is well formed 

 and free; whose pharynx has no lateral walls, owing to enlargement 

 of the primary pair of gill clefts ; and whose blastozooids are incapable 

 of budding, but adhere as a chain from which they eventually break 

 free in groups. 



All that is left of the walls of the branchial chamber (Fig. 457) 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. 453, 456). 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 

 attached 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 



