W. K. BROOKS ON THE GENUS SALPA. 301 



He gives, p. 18, a good description of the segmentation of the side 

 wall of the endodermal tube, but he says that the endoderm and meso- 

 derm are the active agents in the segmentation of the stolon. He does 

 not, however, figure any sections like those in my Plate XLIV, Figs. 5 

 and 11, Plate XXIII, Figs. 6-10, and Plate XXIX, Figs. 4-9 ; these sec- 

 tions show clearly that the active agent is not the mesoderm nor the 

 endoderm, but, as I have stated on p. 78, the ectoderm. 



He states correctly that the structures which I have called the 

 pharyngeal pouches, arise from the side walls of the endodermal tube 

 of the stolon, 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 the species which he studied 

 agree essentially with Salpa pinnata and Salpa cylindrica. While the 

 two pouches are actually right and left, he regards one as dorsal and 

 the other as ventral, and says that the dorsal one is the largest, and that 

 it lies from the first on that side of the stolon to which the salpa belongs, 

 and that it runs through the whole length of the body of the young 

 chain-salpa, and opens, in its middle region, into the horizontal endo- 

 dermal tube of the stolon, so that a neural and a haemal part are distin- 

 guishable. 



His account and figures show that his so-called dorsal pouch is 

 actually the right-hand pouch of a right-hand salpa and the left-hand 

 one of a left-hand salpa. In other respects his account of this pouch is 

 correct, although he fails to discover that all the fundamental anatomical 

 relations of the second pouch are exactly the same, as Plate V, Figs. 1 

 and 2 show. 



He describes the second pouch as ventral and much smaller, and as 

 lacking the oral end, and he says that it loses, long before the dorsal 

 pouch, its connection with the horizontal tube, and becomes a closed 

 vesicle ; and a comparison of his figures with my own will show that he 

 has failed completely in his interpretation of his sections, since all of the 

 points which he notes are superficial and secondary. 



He says that, as the hinder ends of the bodies of the salpse diverge 

 from each other, the small or ventral pouch pushes farther backwards 

 than the larger dorsal one, and that the hindermost end of the dorsal 

 pouch gives rise to a diverticulum, which grows round the hinder surface 

 of the ovary to unite with the ventral pouch. The dorsal pouch gives 

 rise to the pharynx, on the ventral surface of which the endostyle is 

 developed, while the oesophagus, stomach, and intestine are formed from 



