DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 815 
advantageous surroundings have diminished their vigour, they still make active forward 
movements, and often rest on the bottom. The yolk-sac has almost disappeared. An 
almond-shaped mass lies along the floor of the abdominal cavity. The alimentary canal 
appears to be shortened, and still shows the constriction at the pylorus. No anus has 
yet appeared. The urinary vesicle is unaltered. 
Ryper* states that the larval cod has the integument raised above the head, and that 
a large serous cavity or supra-cephalic chamber is formed, which appears to serve as a 
float, but the latter interpretation is doubtful. The fish swims horizontally, but when at 
rest has an oblique position, the tail pointing backward and downward. The sub- 
epidermal space is very prominent in older specimens three or four weeks after emerging, 
and they are then very strong and vigorous, usually frequenting the bottom of the tank, a 
habit inconsistent with Ryprr’s view just stated, and shooting rapidly through the 
water, the large iridescent silvery eyes being the feature most readily seen. They 
dexterously escape from the forceps or other instrument used for their capture, and do so 
with considerable intelligence. The pectorals are large and strong, and the larval cod 
can direct its course with great agility and speed. The mandible and hyoidean apparatus 
project considerably, and the abdomen is hollow and shrunken (PI. X. figs. 5, 5a). 
The lateral view resembles a Chinese caricature of a fish, or a malformed trout, such 
as indicated by Acassiz and Vocr,t this effect being produced by the curvature and 
size of the head. The anus is lateral in position, and has not yet reached the ventral 
margin. 
It occasionally happened that favourable circumstances enabled us to rear an example 
to a somewhat later stage. Thus, for instance, one in which the yolk had wholly dis- 
appeared on the 31st May, though the length was only about 4 mm., presented a marked 
enlargement of the head, chiefly from the great increase of the hyomandibular apparatus 
and the projection of the angle of the jaw. Moreover, the upward slope of the mandible, 
so marked at a later stage, was now characteristic. When viewed ventrally, indeed, this 
formed a high wall on each side of the hyoidean region. The body was comparatively 
massive. The cephalic “vesicle” had disappeared, but the broad marginal fin still 
surrounded the fish, and in the tail fine embryonic fin-rays occurred inferiorly. A few 
also were indicated at other parts of the fin both dorsally and ventrally. Behind the now 
open vent a rounded margin appears in the ventral fin. The pectoral fins are very large, 
and show a finely radiate basal (mesoblastic) region, and a fan-like membranous distal 
portion. The snout in a lateral view is prominent, with a deep hollow above the pre- 
maxillary region. The eyes are large, deeply pigmented, and with the bluish silvery 
sheen so well known at a later stage. Close behind the eyes are the large otocysts with 
the otoliths. One of the most interesting features at this stage is the evolution of the 
coloration of the early post-larval stage out of the four dark bands so characteristic of 
the larval form. At the stage now under consideration the little cod has only two 
* Science, vii. 1886, pp. 26-29 (fig. 1). 
+ Hist. Nat. des Poissons @eau douce, taf. 3b. 
