722 EEPORT— 1900. 



ditious, and subsequently transformed under the influence of tlie internal heat of 

 the earth. This, I think, would be Professor Bonney's view. Finally Lord 

 Kelvin has argued that the life of the sun as a luminous star is even more briefly 

 limited than that of our oceans. In such a case if our oceans were formed fifty- 

 five millions of years ago, it is possible that after a short existence as almost 

 boiling water they grew colder and colder, till they became covered with thick ice, 

 and moved only in obedience to the tides. The earth, frozen and dark, except for 

 the red glow of her volcanoes, waited the coming of the sun, and it was not till his 

 growing splendour had banished the long night that the cheerful sound of running 

 waters was heard again in our midst. Then the work of denudation and deposition 

 seriously recommenced, not to cease till the life of the sun is spent. Thus the 

 thickness of the stratified series may be a measure rather of the duration of simlight 

 than of the period which has elapsed since the first formation of the ocean. It 

 may have been so — we cannot tell — but it may be fairly urged that we know less 

 of the origin, history, and constitution of the sun than of the earth itself, and 

 that, for aught we can say to the contrary, the sun may have been shining on the 

 just-formed ocean as cheerfully as he shines to-day. 



Time required for the Evolution oftJie Living World. 



But, it will be asked, how far does a period of twenty-six millions satisfy the 

 demands of biology ? Speaking only for myself, although I am aware that eminent 

 biologists are not wanting who share this opinion, I answer, Amply. But it will 

 be exclaimed. Surely there are ' comparisons in things.' Look at Egypt, where more 

 than 4,000 years since the same species of man and animals lived and flourished 

 as to-day. Examine the frescoes and study the living procession of familiar 

 forms they so faithfully portray, and then tell us, how comes it about that from 

 changes so slow as to be inappreciable in the lapse of forty centuries you propose 

 to build up the whole organic world in the course of a mere twenty-six millions of 

 years ? To all which we might reply that even changeless Egypt presents us with 

 at least one change — the features of the ruling race are to-day not quite the same 

 as those of the Pharaohs. But putting this on one side, the admitted constancy in 

 some few common forms proves very little, for so long as the environment remains 

 the same natural selection will conserve the type, and, so far as we are able to 

 judge, conditions in Egypt have remained remarkably constant for a long period. 



Change the conditions, and the resulting modiflcation of the species becomes 

 manifest enough ; and in this connection it is only necessary to recall the remark- 

 able mutations observed and recorded by Professor Weldon in the case of the 

 crabs in Plymouth Harbour. In response to increasing turbidity of the sea water 

 these crabs have undergone or are uudergoing a change in the relatire dimensions 

 of the carapace, which is persistent, in one direction, and rapid enough to be 

 determined by measurements made at intervals of a few years. 



Again, animals do not all change their characters at the same rate : some are 

 stable, in spite of changing conditions, and these have been cited to prove that 

 none of the periods we look upon as probable, not twenty-five, not a hundred 

 millions of years, scarce any period short of eternity, is sufficient to account for the 

 evolution of the living world. If the little tongue-shell, Lingula, has endured with 

 next to no perceptible change from the Cambrian down to the present day, how 

 long, it is sometimes inquired, would it require for the evolution of the rest of the 

 animal kingdom ? The reply is simple : the cases are dissimilar, and the same record 

 ■which assures us of the persistency of the Lingula tells us in language equally 

 emphatic of the course of evolution which has led from the lower organisms upwards 

 to man. In recent and Pleistocene deposits the relics of man are plentiful : in the 

 latest Pliocene they have disappeared, and we encounter the remarkable form Pithe- 

 canthropus\ as we descend into the Tertiary systems the higher mammals are met 

 with, always sinking lower and lower in the scale of organisation as they occiu* 

 deeper in the series, till in the Mesozoic deposits they have entirely disappeared, and 

 theur place is taken by the lower mammals, a feeble i'olk, offering little promise of the 

 future ihey were to inherit. Still lower, and even these are gone ; and in the Permian 



