462 Holt — On the Eggs and Larvae of Teleosteans. 



The gut is somewhat large and tubular, except iu the rectal region ; it extends 

 below the notochord a short way beyond the yolk ; the narrow cord-like rectum (n) 

 descends vertically to the marginal imperforate anus (a.), at a short interval from 

 the hind-wall of the yolk-sac. The oil-globules (a g.) are, as a rule, restricted to 

 the posterior region of the yolk, occupying the ventral and ventro -lateral surface 

 of that region, having, as is frequent, undergone a migration backwards from 

 their original positions. 



The marginal fins are somewhat narrow, the dorsal and ventral being about 

 •12 mm. each, except at the anterior extremity of the ventral, which descends on 

 to the postero-ventral border of the yolk-sac, becoming thus somewhat deeper. 

 The dorsal commences at the otocystic region ; the caudal is short and rounded, 

 with no embryonic rays. The pectoral fins have not appeared. The notochord 

 is multi-columnar, with small cells. 



The pigment, now a bright-orange colour (brown by transmitted light), occurs 

 in small chromatophores over the head, along the back, and ventral post-anal 

 region, over the yolk-sac, and on the posterior part of the gut, and at the anus. 

 It forms a conspicuous bar {p-h-) across the trunk at the commencement of the 

 posterior third of the total length. Cliromatophores occur also on the dorsal, and 

 sparingly along the edge of the ventral fin. 



The total length at this stage is2'02 mm., of which the pre-anal region occupies 

 •895 mm., the anus («.) being slightly anterior to median. It is probable that there 

 is slight variation in the length of the larva on emerging. 



A specimen about a day old (fig. 47), has a total length of 2*14 mm., the 

 increase being entirely in the post-anal region. The yolk is slightly reduced. 



At about two days old (fig. 48) the total length is the same as in the last stage. 

 The yolk is further reduced, and the oil-globules are fewer in number. The snout 

 is more forwardly directed, and the pineal body is conspicuous. The mid-brain 

 has gained slightly in dorsal prominence. The otocysts are larger and ventrally 

 convex. They have undergone a slight upward rotation on their posterior ends, 

 and, by the shortening up of the hind-brain, are carried nearer to the eye. 



The invagination of the stomatodeum has commenced. The pectorals have 

 appeared as semicircular folds of epiblast (their bases parallel to the notochord), 

 midway between the snout and the anus. The gut is dilated more conspicuously 

 in the region of the future stomach (5.), and its thickened tubidar character has 

 extended some way down into the rectum. The chomatophores have now become 

 stellate, and another pigment bar (p.b.) has appeared across the trunk midway 

 between the anus and the bar noticed in the newly-hatched larva. The chromato- 

 phores of the yolk-sac are fewer, but larger than formerly, and those on the edge 

 of the ventral fin have disappeared. The dorsal fin has extended forward to the 

 mid-brain, and is much expanded, as are the ventral and short pre-anal tins. 



