466 Holt — On the Eggs and Larvce of Teleosteans. 



The structure of the notochord {no.), unicolumnar throughout at this stage, is 

 clearly visible, and there is a broad marginal fin. 



I was only successful in hatching one egg of this species, viz. one obtained on 

 the 25th June. I examined the larva on the 29th June (figs. 28 and 29), when it 

 appeared to be somewhat older than Agassiz and Whitman's C. aclspersus of 

 twenty-four hours {oj). cit., PI. ix.). The total length is 2-855 mm. The pre-anal 

 length is 1"37 mm., and there is an interval of •62 mm. between the yolk and the 

 anus; the post-anal length is 1'485 mm. 



There are five pairs of lateral sense organs {l.s.o.) as in C. adspersus, of which 

 the first pair occupies the same position as in the American species, viz. between 

 the eyes and otocysts. The three remaining pairs, however, lie further back than 

 in the newly hatched C. adspersus, the second pair lying between the end of the 

 yolk and the anal region, whilst the last three are placed at equal distances along 

 the post-anal region. They represent probably some of those more numerous 

 organs shown by Agassiz and Whitman {op. cit.) in a larva some hours after 

 hatching (PI. ix., fig. 33). The third and fourth pairs are not quite sym- 

 metrical. 



The greater part of the head projects forward in front of the yolk, terminating 

 in a blunt snout. There is as yet no mouth. The pineal is easily seen, as are 

 the precocious nasal sacs {ol.), from which the nasal valves {n. v.) already project 

 clear of the contour of the head (fig. 30). The cerebellar fold is small. The 

 otocysts {at.) are sub-circular and small, and as yet remote from the large unpig- 

 mcnted eyes. The pectorals (/>./.) are visible as largish, semicircular folds of 

 the lateral epiblast about half-way between the snout and anus. 



The gut is slightly dilated below the pectoral fins. It runs back as a thick- 

 walled tube below the notochord to the anal region, at which point it sends down 

 a solid translucent cord-like limb (r.) almost vertically, to the marginal and imper- 

 forate anus («.). The urocyst is not visible. 



The notochord {no.) presents the same remarkable structure as in C. adsp)ersus. 

 Its anterior third, i. e. the part overlying the yolk, is unicolumnar. At the com- 

 mencement of the middle-third two cells begin to make their appearance in the 

 same plane of transverse section, a condition which persists as far back as the 

 caudal extremity, where, as is frequently the case in larval fishes, the notochord 

 is irregularly unicolumnar. The cells of the anterior unicolumnar region have not 

 the same bubble-like structure as is met with in the herring and sprat. 



The dorsal marginal fin rises a little behind the otocyst and gradually attains 

 its greatest height, a little more than that of the body, opposite the anus. The 

 ventral fin is of the same dimensions as the dorsal, both tapering insensibly into 

 the short and almost lanceolate embryonic caudal fin. Anteriorly the rectum {r.) 

 cuts off a pre-anal segment {p. a.f.) from the ventral marginal fin, the margin of 



