130 Mr. W. K. Bruoks on (he 



cesophagus, and the stomach and intestine are developed from 

 its blind end. In all the species I have studied the intestine 

 bends to the left past the stomach, to open dorsally into the 

 median atrium, and the digestive tract assumes the form of a 

 figure 8, which is persistent in most species, although in Salpa 

 pinnata the intestine gradually moves downward as develop- 

 ment advances, until it finally becomes ventral to the stomach. 

 As the gut arises, in both right-hand and left-hand Salpte, 

 from the right pliaryngeal pouch, and since the distortions 

 which are produced by pressure and by the changes of position 

 affect the right-hand pouch of a right-hand Salpa just as they 

 affect the left-hand pouch of a left-hand Salpa, and since they 

 affect the other pouches in quite a different way, the history 

 of tlie gut in a right-liand Salpa is superficially very different 

 from that of a left-hand Salpa, although fundamentally they 

 are exactly alike. 



While Salensky, in his first paper on the budding of Salpa, 

 describes the endodermal tube, he says that it takes no part 

 in the construction of the Salpa?, and that their digestive 

 organs are derived from that ])art of the stolon which I have 

 called the genital rod. Seeliger, a few years later, pointed 

 out Salensky 's error, which he has himself admitted in a 

 recent paper (' Pyrosoma,' p. 78). 



Seeliger's account of the origin of the endodermal tube and 

 digestive organs is given on pp. 14, 18, 26-34, and 54-62 

 of his paper on the budding of Salpa. He shows (p. 14) that 

 the endodermal tube of the stolon is derived from the pharynx 

 of the embryo, with which it at first communicates, although 

 he says that this connexion is soon lost ; while my observa- 

 tions show that it is persistent at all stages in the history of 

 the stolon of Salpa pinnata and Salpa cylindrica. 



He gives (p. 18) a good description of the segmentation of 

 the side-walls of the endodermal tube, but he says that the 

 endoderm and mesoderm are the active agents in the segmen- 

 tation of the stolon ; wliile my own observations show clearly 

 that the most active agent is not the endoderm nor the meso- 

 derm, but the ectoderm. 



He states correctly that the structures which 1 have called 

 llie pharyngeal pouches arise from the side-walls of the endo- 

 dermal tube, and that two of them enter into the body of each 

 Salpa ; but here the agreement between his account and my 

 own observations ends, although his figures show clearly that 

 tlie species which he studied, Saljja dcmocratica, agrees in all 

 essentials with those which 1 have studied. 



While the two pharyngeal pouches are actually right and 

 left, he regards one as dorsal and the other as ventral, and 



