152 “TERRA NOVA” EXPEDITION. 
difficult to assign any reason for the stalked eyes of some early larvae (Stomiatidae, 
especially Stylophthalmus), unless it be conceded that they may enable the larva to 
see in all directions and help it to maintain a balance, and, as it is so small and not yet 
an active swimmer, are not likely to be injured or to impede its progress. 
Defence.—Many pelagic larvae have the bones of the head, and especially the 
praeoperculum, armed with strong spines, no doubt defensive. This is well exemplified 
by Thyrsites (p. 144, Pl. VIII, figs. 1-3), Platycephalus (p. 146, Pl. X, fig. 4) and 
Ancylopsetta (p. 146, Pl. IX, figs. 3, 4). The precocious development, probably for 
defensive purposes, of the spinous dorsal and pelvic fins in Thyrsites has already been 
referred to. 
5. SYSTEMATIC IMPORTANCE OF LARVAL CHARACTERS. 
Except in a few groups, of which the Apodes are the most notable example, there 
are no features that characterize pelagic larval fishes as belonging to one order or 
another, and it is not easy to determine their systematic position unless they are 
sufficiently advanced towards the structure of the adult fish. In all cases the number 
of myotomes and of fin-rays, if these be developed, are of the greatest help ; with these 
as a guide one may, by a patient process of trials and eliminations, determine 
specifically some most puzzling examples, as, for instance, the post-larval Oda 
balteatus, described and figured above (p. 143, Pl. VIII, fig. 4). Although it does not 
appear that the diagnostic characters of the different orders are likely to be strongly 
reinforced by larval features, yet the study of a series of larval and young fishes, such 
as those collected by the “Terra Nova,” confirms and in no degree modifies ideas as to 
the relationship of the Teleostean orders and families derived from the study of the 
morphology of the adult fish. 
The pigmented patches on the gut of the Sudidae and Synodontidae (Pl. VII, 
fies. 1, 2, 4), the armature of the head in the Platycephalidae (PI. X, fig. 4) and 
Triglidae, are examples of similar larval characters in related families. The 
development of the anal fin before the dorsal in the Iniomi, the migration of the dorsal 
in the Clupeidae, Albulidae, etc., may be cited as examples of developmental features 
common to a series of related families. 
