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. 



Ryder* 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 Ryder'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 Agassiz and VoGT,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 iu 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). 



t Hist. Nat. des Poissons d'eau douce, taf. 36. 



