Page:The Zoologist, 4th series, vol 1 (1897).djvu/431

Rh present themselves there is a loose tendency to phylogenetic speculation. This last may temporarily satisfy our ignorance, but yet is an unstable platform to rest on where practical issues are at stake.

Necessarily many of the researches now in progress appear superfluous or insignificant, but science abounds with instances of seeming trifles leading to unexpected beneficial results. It cannot be affirmed with absolute certainty that there has been material increase in British fisheries since the advent of the laboratory and out-of-door investigations. But there is no gainsaying the fact that a sound foundation has been laid for a study of their economy; witness Mcintosh and Cunningham's volumes aforesaid. Take, for example, investigations of embryotic and postlarval conditions: it is a long jump from 0 to over eighty species to be recorded.

The spawning grounds, the periods of spawning, and the varied lengths of the spawning process in different fish, are in many cases far better understood, whilst it is pretty well proved that temperature has a manifest effect on the duration of hatching, a fact established by Higginbotham (1850) in experiments on the Frog, and now shown likewise to be the case in fish-eggs. Migratory habits are gradually getting law-evolved. As to cases in point, there is that of the to-and-fro movement from offshore to inshore, and the reverse. Of a certainty it can now be said of some fish, that on hatching the larva and post-larva uniformly and gradually make for shore or shallow water, there to spend their young stage, to retreat again to deep water on becoming older, and this in a definite course. There is regular congregation and migration during spawning season, partial dispersion thereafter. Search for food assuredly induces wandering habit, and atmospheric changes drive to greater depths. The factors conducing to erratic wholesale emigration, or the sudden departure from a long frequented spot or area, each fish's particular enemies, and their diseases aside from effects of parasites, are still sub judice.

Probably there is no more promising field still requiring exploration on British shores than that of the surface organisms,