LARVAL AND POST-LAJIVAL FISHES— REGAN. 110 



range do not ]iave a [lartirularl}' ImiLi,- larval life l>ut that the \-(aiii^ tislics mav 1)0 

 oceanic. 



Of the species dealt with in this report three iiia\' lie selected lo illiislrare this. 



(1) Xofothcnia mdcrorvpliaUi (p. 130), a species of the shallow water heiithos; 

 this is known from the Magellan and New Zeal.-ind districts and IVoni Kcrguclcn : 

 oti' the last-named the ■'Challenger" obtained \'oung fishes, 40 mm. long, swimminn' 

 at oi' near the surface. 



(2) Heiii'irlKinijiliiis iiinfusi'nitiis (p. 142) ranges from Florida to Itio de .laneiro, 

 and belongs to a genus of lierliivorous fi.shes that swim at the surface near the coast. 

 The ciiptui'e of a y(anig tish. 10 mm. long, far out in the iVtlantic, is of interest, 

 as //. luciirti, Cuv. ,-iml \'al.. from Algeria, is believed to be tlie same species. 



(:!) Limiiirlitlti/s fiisc'nitns (p. 143). Previously recorded from rock-pools near 

 Sydney and at J.ord 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 midwav between these localities. 



I'^nrtliei' examples are Srof/nii'i/ii ([). 145) and ( 'rj/jifofomiis iis/iis (p. 14.'i). 



ll ma\' be I'Cgarded as nearh' c(>i'tain that wlien a species of coast fishes oi-eurs 

 in ai-eas separated from each other by wide exj^anses of the ocean, it has ;i pelagic 

 phase in its life history of sutMcient duration to enable it to travel or to be carried from 

 one such area to another. In some fishes {Bofhu-s, Apodes) this pelagic stage ends 

 when the larva acquires the structure and habits of the adult fish, but in other cases 

 it seems that tlie voung tishes. essentially similar to the adults in structure, may 

 differ from them in habits and swim across the (u-ean. 



2. THE RECAPITULATIUN THEORY. 



It is well known that the truth of the theory that ontogen}' repeats phylogeny 

 is shown by almost every Teleostean tish in the development of its caudal fin. which 

 is at first ventral and then becomes terminal. 



Two rathei' puzzling develo[)mental features, the migration Ibrwai'ds of the 

 dorsal fin in the Clupeidae and the migration backwards of the anus in An/c/i'/iis^ 

 I'll mil- I'ls^ et(/., may possibly be explained by the same theory. 



In the Clupeidae, and the closely-related Elopidae and Albulidae. which are the 

 most generalised lining Teleosts, the (h)rsal fin is completely formed on ilu' ])osterior 

 part of the back and tlien travels forward to its permanent position. The earliest lishes 

 that can be regarded as ancestral to the Clupeoids are the palai'ozoie I'alaeouiscidae : 

 in this family the dorsal fin was placed posteriorly, usually abovi' ilie an.d. Ne.\t 

 come the Semionotidae, which are a big step nearer the Teleosteans. ami then the 

 Pholidophoridae, which may be regarded as the immediate ancestors of the Clupeoids; 

 in both these mesozoic families, and espei-ialh' in the Semionotidae. ilic dorsal tin is 

 placed well backward and in a nundierof the genera is at least paitlx' opposed to the 



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