W. K. BROOKS ON THE GENUS SALPA. 77 



and to their cellulose mantles. The nerve tube gives rise to the ganglia. 

 The lateral portions of the endodermal tubes give rise to the corres- 

 ponding halves of the pharynx ; and the oesophagus, stomach and intes- 

 tine are derived from the one on the right side. The perithoracic tubes 

 give rise to the cloaca and to the cloacal portions of the two gill-slits by 

 which it opens into the pharynx. 



The body cavity consists, in part at least, of diverticula from the 

 blood spaces, and it is lined by their endothelium. The muscles and the 

 stoloblast, or the equivalent of the eleoblast, are derived from mesoderm 

 cells from both sides of the stolon. The heart and pericardium are 

 probably formed from some of the mesoderm cells on the right side. 

 The eggs and their follicles and fertilizing ducts, and the testes, are 

 derived from the genital rod. 



