Origin of the Organs o/Salpa. 137 



says that the dorsal one is 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 endodermal tube of the stolon, so that a neural and 

 a hajraal part are distinguishable. 



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

 is actually the right pouch of a right-hand Salpa or the left 

 pouch of a left-hand one. 



In other respects his account of the origin and primary 

 relations of this pouch is correct, although he fails to discover 

 that the historj^ of the second pouch is exactly the same. 



He describes the second pouch as ventral and much smaller 

 and as lacking the oral end, and he says that it looses long 

 before the dorsal pouch its connexion with the horizontal tube, 

 and becomes a closed vesicle, and that, as the liinder ends of 

 the bodies of the Salpa diverge from each other, the smaller 

 ventral pouch pushes further backwards than the larger dorsal 

 one, and that the hindermost end of the dorsal pouch gives 

 rise to a diverticulum which grov/s round the hinder surface 

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

 pouch gives rise, he says, to the pharynx, on the ventral 

 surface of which the endostyle is developed, while the oeso- 

 phagus, stomach, and intestine are formed from the rudiment 

 which has arisen at the posterior end by the union of the two 

 pouches. 



It is not necessary to enter into a more minute analysis of 

 his description, for comparison will show that he has been 

 misled by his erroneous conception of the primary position of 

 the buds, and has mistaken the symmetrical right and left 

 pouches for unpaired dorsal and ventral ones. 



His more recent account of the origin of the post-pharyngeal 

 gut of Pyrosoma (' Pyrosoma,' pp. 28-25) is very similar to 

 what I have found in Salpa ; for he says (pp. 615-622) that 

 while it arises as a pair of folds from the phaiynx, these soon 

 unite to form an unpaired diverticulum, which afterwards 

 becomes differentiated into oesophagus, stomach, and intes- 

 tine ; that its pharyngeal end becomes the oesophagus, while 

 the intestine arises from its blind end and ultimately acquires 

 an anal opening into the median atrium. 



Salensky's account of the origin of the gut in Pyrosoma is 

 quite different, however, for he says (' Pyrosoma,' pp. 69- 

 72) that it is bilateral in origin and arises as a pair of folds 

 from the sides of the aboral end of the pharynx, which unite 

 with eacli other to form a horseshoe-shaped canal. If I 

 understand his description, he holds that the rigiit fold forms 



