LARVAL AND POST-LARVAL FISHES—REGAN. 149 
range do not have a particularly long larval life, but that the young fishes may be 
oceanic. 
Of the species dealt with in this report three may be selected to illustrate this. 
(1) Notothenia macrocephala (p. 130), a species of the shallow water benthos ; 
this is known from the Magellan and New Zealand districts and from Kerguelen ; 
off the last-named the ‘“‘ Challenger” obtained young fishes, 40 mm. long, swimming 
at or near the surface. 
(2) Hemirhamphus wnifasciatus (p. 142) ranges from Florida to Rio de Janeiro, 
and*belongs to a genus of herbivorous fishes that swim at the surface near the coast. 
The capture of a young fish, 10 mm. long, far out in the Atlantic, is of interest, 
as //, picarti, Cuv. and Val., from Algeria is believed to be the same species. 
(3) Limnichthys fasciatus (p. 148). Previously recorded from rock-pools near 
Sydney and at Lord Howe Island; the pelagic young of this little fish were taken 
by the “Terra Nova” to the north of New Zealand, near the*Three Kings Islands, 
and midway between these localities. 
Further examples are Scorpaena (p. 145) and Cryptotomus ustus (p. 143). 
It may be regarded as nearly certain that when a species of coast fishes occurs 
in areas separated from each other by wide expanses of the ocean, it has a pelagic 
phase in its life history of sufficient duration to enable it to travel or to be carried from 
one such area to another. In some fishes (Bothus, Apodes) this pelagic stage ends 
when the larva acquires the structure and habits of the adult fish, but in other cases 
it seems that the young fishes, essentially similar to the adults in structure, may 
differ from them in habits and swim across the ocean. 
2. THE RECAPITULATION THEORY. 
It is well known that the truth of the theory that ontogeny repeats phylogeny 
is shown by almost every Teleostean fish in the development of its caudal fin, which 
is at first ventral and then becomes terminal. 
Two rather puzzling developmental features, the migration forwards of the 
dorsal fin in the Clupeidae and the migration backwards of the anus in Notolepis, 
Paralepis, ete., may possibly be explained by the same theory. 
In the Clupeidae, and the closely-related Elopidae and Albulidae, which are the 
most generalised living Teleosts, the dorsal fin is completely formed on the posterior 
part of the back and then travels forward to its permanent position. The earliest fishes 
that can be regarded as ancestral to the Clupeoids are the palaeozoic Palaeoniscidae : 
in this family the dorsal fin was placed posteriorly, usually above the anal. Next 
come the Semionotidae, which are a big step nearer the Teleosteans, and then the 
Pholidophoridae, which may be regarded as the immediate ancestors of the Clupeoids ; 
in both these mesozoie families, and especially in the Semionotidae, the dorsal fin is 
placed well backward and in a number of the genera is at least partly opposed to the 
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