954 On the Gsophageal Teeth of the Stromateide. 
the general direction of the branchial arches. As in the last 
case, the toothed epithelium of the upper branchial elements 
projects backwards as a stout lobe into the cesophagus, between 
the opening of the sacs, and is followed by several series of 
smaller lobes which line the interior of the sac, as in Psenes 
capensis. 
Material was not available for the further examination of 
this and other types, which would no doubt throw further 
light on the structure and homology of these sacs, which we 
may, however, reasonably conclude, from the above evidence, 
are not strictly cesophageal, but are derived from an extension 
backwards of pharyngeal epithelium in the form of two 
pouches. There seems to be at least two distinct types, in 
which the lining of the sacs is derived from the toothed 
epithelium of the pharyngo-branchials, and the other in 
which it is derived from the raker-bearing elements of the 
gill-arch. The-distinction may also prove to be of systematic 
importance, in which case species resembling Psenes capensis 
would be generically separated from species resembling 
P. natalensis in respect of the nature of their cesophageal 
teeth, 
The origin of the conspicuous paired saccular outgrowths 
lined by pharyngeal epithelium is of interest, as they may 
date from atime in the phylogeny of the Teleosts when the 
gill-slit behind the fifth branchial arch began to close up, and 
may now be all that remains of this gill-slit. ‘Their develop- 
ment and further comparative study of their structure in 
various groups (they also eccur in the Tetragonuridee) might 
throw some light on this point. Certainly in Nomeus they 
bear a striking, if superficial, resemblance in position to a 
gill-slit. 
~The physiological significance of the “cesophageal teeth 
which are found in these fishes is of interest, and has doubtless 
some connexion with the nature of their food. ‘The teeth of 
the jaws are poorly developed, and in some there are gill- 
raker-like structures below the pseudobranchie. -It is known 
that some feed on meduse. Nomeus—the well-known 
Portuguese man-of-war fish—is said to find protection from 
its enemies by hiding under the poisonous tentacles of the 
Portuguese man-of-war Physalia, and perhaps securing the 
jackal’s share of its food; but it may be suspected that its 
object there, among medusve- producing gonophores as well as 
poisonous tentacles, is not such an innocent one. The nature 
of the food may again be associated with another peculiar 
feature, well developed in some. Pores are described as 
occurring on the surface of the body, and these, when traced 
