486 A. T.. MASTERMAN. 
ing to the age of the larva. These vacuolations are identical 
with those described in the pharynx of Actinotrocha, and 
are apparently the first stages in the production of chordoid 
tissue found in the adult pharynx of Balanoglossus and 
Cephalodiscus. Morgan gives a figure of the cesophagus, 
in cross-section, of the youngest Bahama larva. It shows the 
same condition as regards the arrangement of the cilia, i.e. 
dorsal and ventral ciliated areas and an entire absence of 
cilia from the lateral regions. 
-No allusion to this structure is made in the text, and the 
later stage seems according to the figures to have a different 
disposition of the cilia. Morgan makes no allusion to the 
vacuolation. Larval stages can be obtained which show all 
the main features here outlined without any trace of the 
vacuolations, which appear to arise generally at a late stage. 
The pharynx of Tornaria (at this stage) therefore con- 
sists of a long funnel-shaped tube, narrowing inwards and 
depressed dorso-ventrally at the outer end. Its dorsal and 
ventral surfaces are ciliated throughout, and in the lving 
condition tend to become depressed, especially the ventral 
wall, into grooves. Down each side there runs a lateral 
eroove, the cells of which are non-ciliated and tend to become 
vacuolated. Hach of these lateral grooves passes out at the 
corner of the mouth into the vestibule. This condition 
reminds one irresistibly of the pharynx of Cephalodiscus, 
as will be explained later. The two lateral grooves corre- 
spond with the pleurochords in Cephalodiscus, with the 
difference that they do not terminate in closed tubes or 
pharyngeal clefts, but in oral grooves. Down the centre of 
this pharynx food-particles can be seen to pass in a current 
which. sets steadily towards its inner termination. I have 
failed to trace the return current of water chiefly because it 
is devoid of food particles, and. is very difficult, if not 
impossible, to see. he particles gather in a batch at the 
end of the pharynx, the entrance of which to the stomach is 
closed. It is difficult to understand how the water can find 
