136 Mr. W. K. Brooks on the 
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 Salpe, 
from the right pharyngeal 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 the gut in a right-hand 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 Salpe, and that their digestive 
organs are derived from that part 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; while 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 I have called 
the 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 
the species which he studied, Salpa democratica, agrees in all 
essentials with those which I have studied. 
While the two pharyngeal pouches are actually right and 
left, he regards one as dorsal and the other as ventral, and 
