SUNFISHES. 
623 
occasions, and the late development of the caudal fin 
has been fully demonstrated (fig. 154). According to 
Lutken®, however, we have a still earlier developmental 
Fia;. 154. 
Larvae of Ortliagoriscus mola; A. at a length of 18 mm., 
B . at a length of 32 min. After Gunther. 
stage of Ortliagoriscus in the form named by Richard- 
son Ostracion loops (fig. 155), after the larval speci- 
mens taken at the surface of the South Atlantic and 
Fig. 155. 
Ostracion hoops, Richardson. 
After GUnther. 
figured by Hooker. These larva; are of a still more 
curious form, with their large eyes and their equipment 
of large spines, such as those we have seen above on the 
heads of several Acanthopterygian larvae, notably within 
the great series of the Scombromorphs, and with small 
spines besides on the dorsal side. The difference be- 
tween them and Kolreuter’s larvae, however, is not so 
great as to prevent us from easily recognising the cor- 
responding position of the large spines. As in the 
younger of Kolreuter’s larvae we here find one large 
spine at the middle of the forehead between the eyes; 
three at the sharp dorsal margin, the hindmost of which, 
just in front of the dorsal tin, is the largest; one 6 on 
each side above the eyes, as well as on each side of 
the hind part of the body between the dorsal and anal 
fins. Whether the other spines correspond exactly in 
both larvae, is a more difficult point to decide. The 
4 
caudal tin is still less developed than in the younger 
of Kolreuter’s larvae. As the development advances, 
the large spines are said to become comparatively 
smaller, but the small spines, the papillae with radiat- 
ing striae, to extend densely and evenly over the tvhole 
body. The transition to the Ortliagoriscus form is thus 
not far distant 0 . 
If we compare these youngest forms of Ortliago- 
riscus with the normal forms of piscine larvae, the 
greatest difference lies in the fact that here the caudal 
tin, which otherwise is the first fin to appear — as it 
also is the original organ of motion in all vertebrates — , 
is developed last of all the fins. This difference has 
left its mark not only on the structure of the skeleton, 
but also on the development of the muscles. Here the 
original and, in later life, the most powerful organs of 
motion are the dorsal and anal fins. Their supporting 
bones (the interneural and interhsemal bones) and their 
motory muscles exercise a determinant influence on 
the development of the whole trunk- 
In dissecting an Ortliagoriscus d we have first to cut 
through the enormously thick skin, which is lined with 
a strong tendinous membrane ( aponeuros ). Within the 
latter, on the sides of the body, w6 make the remark- 
able observation (fig. 156) that the muscles most highly 
developed in other fishes, the large lateral muscles of 
the body, are here apparently wanting. Between the 
spinal column and the skin runs, as usual, in a hori- 
zontal direction, a fibrous membrane (sf), which here 
is especially strong, and divides the visible muscular 
mass, just as in other cases it divides the large lateral 
muscles of the body, into two halves, an upper and a 
lower. But by far the greater part of this muscular 
mass is here composed of the flexors of the dorsal ( mpd ) 
and anal ( mpa ) fins. The flexors of the dorsal fin, 
divided into two layers of different colour and firmness 
— a surface-layer and an under-layer — run from the 
occiput, from the spinal column with its superior pro- 
cesses and interneural bones, and from the upper sur- 
face of the horizontal fibrous membrane (sf), and are 
attached by a special sinew to each side of the basal 
vol. VIII (1871), p. 320, note. 
Powerfully magnified. 
u See GOnther, Ann., Mag. Nat. Hist., ser. 
6 In K6 lreuter’s larva two. 
c According to Lutken’s opinion of KOlreuter’s larvae. Still we should observe that the larvte of Diodon correspond just as closely 
to Richardson’s larvae, especially in the position of the large spines; but in the former the end of the notochord projects between the dorsal 
and anal fins. A larva of this description, 2 inm. long and of ellipsoidal form, which was taken at the surface “between Java and the Cape of 
Good Hope,” has been obtained by the Royal Museum through Captain P&hl of Hamburg. In the same jar (and therefore taken probably at 
the same time) lay another larva, 4 mm. long and of more distinct Diodon form, but still, like the preceding one, with the dorsal and anal 
fins and the tip of the tail between them all situated on the ventral side. 
d Cf. Wahlgren, Nagra anteckningar om en stor klumpjisk , Lunds Univ. Arsskrift, tom. IV. 
Scandinavian Fishes. 
79 
