Origin of the Organs of 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 hemal 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 history 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 hinder 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 grows 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 ceso- 
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. 23-25) 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 pharynx, these soon 
unite to form an unpaired diverticulum, which afterwards 
becomes differentiated into cesophagus, stomach, and intes- 
tine; that its pharyngeal end becomes the cesophagus, 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 each other to form a horseshoe-shaped canal. If I 
understand his description, he holds that the right fold forms 
