DEALFISHES. 
311 
equal to that of the body. The abdominal part of the 
body plus the head is about equal in length to the caudal 
part, but. the base of the ventral tins still remains just 
behind and below that of the pectoral. Four of the rays 
in each ventral fin are already elongated. The caudal fin 
has begun to form the first rudiments of its true rays 
below the end of the notochord, which is curved up- 
wards at the tip, though as yet only slightly. Exter- 
nally, however, the tip of the tail is still symmetrical, 
with a. lobate extension of the embryonic vertical fin 
itself on the skin. In other respects the larva is only 
slightly changed from the appearance it had at a length 
of 9 mm.; but the development of the embryonic pec- 
toral fins is now arrested, their brachiate base showing 
signs of reduction. The five occipital rays of the dorsal 
fin and the three outer ventral rays have attained a 
length more than double that of the body, but are 
united to a fairly great extent at the base by the fin- 
membrane. The three inner rays of the ventral fins 
gradually diminish in length. The vent lies at the end 
Fig. 79. Caudal fin of a Trachypterus iris 26 mm. long, from Messina, d, embryonic vertical fin of the back; 
v, embryonic vertical fin of the ventral edge; cli, chorda dorsalis. 
which is about equally large above and below the end 
of the notochord; but only the lower lobe is furnished 
with rudimentary rays, while in the upper we find only 
the primary fibrillse, which are destined soon to dis- 
appear, together with the whole of this lobe. Chro- 
matophores are scattered both on the raised occiput 
and the sides of the abdominal cavity. 
In the next stage of the development described by 
Emery (fig. 78), the larva has attained a length of 16 
mm. The silvery colour has now begun to deposit 
of the second third of the length of the body. The 
embryonic vertical fin is still present along the ventral 
margin, but there are no rudiments of true rays in front 
of the caudal fin, and there seems to be no rudiment 
of a true anal fin. The caudal fin, on the other hand, 
has passed through a great part of its early alterations. 
This fin originates, here as in all Teleosts, at the 
ventral part of the caudal end of the embryonic (larval) 
vertical fin, but in front of the end of the notochord. 
It thus belongs originally to the same division as the 
