to these Mesozoic and Palaeozoic times ; and we know not yet what further resemblances to old forms of life may yet be detected in the vast field just opened to us.
The present explorations, full of interest and valuable as they are, are insignificant compared with the vast area of the ocean ; so that when we look at what has been accomplished in these tentative researches, we can only take them as indicative of the rich mine that yet remains to be explored, and look forward to discoveries that will probably modify and throw much new light on the relations between the marine life of the present and the past.
One of the great subjects which these researches may put before us in this new light is, that instead of the imperfect record which geology usually gives us of the life of the old world, with its interrupted succession in local descent, we may have, if the hypothesis of an area continuously submerged from the Cretaceous period should prove true, the lineal descendants of some portion of those creatures which lived in the Chalk seas. If so, naturalists will be able to see the exact amount of changes wrought, and to study in what direction they have been effected. We shall see the effects of continuity in time in conjunction with continuity of conditions, and whether any and what new forms have been evolved, and where no progress has been made. We see already that the Foraminifera, Sponges, and Echinoderms claim relationship with their fossil antetypes, though in an unequal degree. How will the fully ascertained results agree with the theory of Natural Selection ? Beautiful, ably handed, and ingenious as this theory is, it seems to me — I will not say to fail, because I am not competent to pronounce on the natural-history bearings ; but it fails to satisfy me. Natural Selection is founded primarily on Sexual Selection ; and this latter seems to me an implant so strong, and to have an object so definite, viz. that of maintaining the species in full vigour, strength, and health, that, in the absence of any more direct evidence to the contrary, I would believe in the force of this law of life to perpetuate the special type unaltered, rather than in a divergent natural selection, leading, concurrently with changes of condition, to aberrant forms. We have had curious and remarkable evidence of elasticity of structure in certain directions ; but does not the rebound, in almost all cases, show the existence of a spring which, while it admits of considerable play, tends to readjustment as soon as the restraint is removed. That there have been gradual changes in structure in all classes of animal
