DEVELOPMENT AND LIFE HISTORY OF SOME TELEOSTS 
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The finfold no longer remains continuous, as the caudal fin is fairly well developed 
and the bases of the dorsal and anal fins have become indefinitely outlined and some 
of the rays have become differentiated. Pectoral fins, too, are evident, but the 
ventrals remain undeveloped. The notochord is curved upward posteriorly, giving 
the tail a heterocercal appearance. The mouth remains nearly vertical as in younger 
fish. The body is unpigmented, except for a few dark chromatophores on the 
median ventral outline of the body and tail, the last one of these dark spots, situated 
near the end of the anal base, being the largest (fig. 43). 
Specimens 5.0 mm long .— The shape of the body is essentially as in specimens 
4.0 mm long. The mouth, however, is not quite as nearly vertical as in the smaller 
fish. The development of fins has progressed rather rapidly, the caudal, soft dorsal 
and anal being sufficiently developed to show the rays rather definitely and it is 
now possible to enumerate the rays of the second dorsal and the anal quite definitely 
which is a great help in identification. The first, or spinous dorsal, is partly developed 
in some specimens, but it is impossible to count the spines accurately. The pectoral 
fins are plainly evident but without distinct rays. The ventral fins, however, are 
still undeveloped. The air bladder remains slightly visible, microscopically, through 
the abdominal walls as an area which is slightly more transparent than the abdomen 
is elsewhere. The notochord is still turned upward posteriorly and pigmentation 
remains essentially as in 4.0 mm specimens (fig. 44). 
Specimens 7.5 mm long .— The body remains shaped essentially as in 5.0-mm 
specimens, that is, compressed and slender, the depth being contained in the length 
to base of caudal fin about 6.25 times. The fish has a somewhat different appearance, 
however, at this size, mainly because of the rather pointed snout; for the mouth, 
although still superior, has become rather oblique with a somewhat pointed projecting 
mandible, as seen in a lateral view. The muscular rings on the body remain rather dis- 
tinct, but the heterocercal character of the tail generally has disappeared. The 
air bladder remains visible, microscopically, through the body wall as a somewhat 
lighter area. The development of the fins has progressed slowly. The spinous 
dorsal is not yet evident, but the ventrals now appear as a short tuft of membrane 
