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Show 420 DARWINISM CliAP. elaboration .that the outer and inner parts of these arc necessarily subject to different conditions ; and that the outer actions of air or water lead to the formation of integuments, and sometimes to other definite modifications of the surface, whence arise permanent differences of structure. Althongh in these cases also it is very difficult to determine how much is due to direct modification by external agencies transmitted and accumulated by inheritance, and how much to spontancons variations accumuhttcd by natural selection, the probabihtic:-; in favour of the former mode of action arc here greater, because thero is no differentiation of nutritive and reproductive cells in these simple organisms ; and it can be readily seen that any change produced in the latter will almost certainly affect the next gencration.1 'Ve are thus carried back almost to the origin of life, and can only vaguely speculate on what took place under conditions of which we know so little. 1'he American School of Evolutionists. The tentative views of Mr. Spencer which we have just discussed, are carried much further, and attempts have been made to work them out in great detail, by many American natumlists, whose best representative is Dr. E. D. Cope of Philaclclphia.2 This school endeavours to explain all the chief modifications of form in the animal kingdom by fundamental laws of growth and the inherited effects of use and effort, returning, in fact, to the teachings of Lamarck as being at least equally important with those of Darwin. The following extract will serve to show the high po;ition claimed by this school as original discoverers, and as h:wing made important additions to the theory of evolution :- " 'Vallace and Darwin have propounded as the canso of modification in descent their law of natural selection. This law has been epitomised by Spencer as the 'survival of the fittest.' This neat expression no doubt covers the case, lmt it leaves the origin of the fittest entirely untouched. JJ:n·win assumes a 'tendency to variation' in nature, :tnc.l it i: plainly 1 This explanation is derived from Weismann's Theory of the Continu ity of the Germ-Plasm as summarised in Natu1·e. 2 See a collection of his e .. says under the title, J'he Origin nf the Fittest : Essays on Evolution. D. Appleton and Co. New York. 1887. XIV FUNDAMENTAL PROBLEM 421 necessary to do this, in order that materials for the exercise of a :election should exist. Darwin and Wallace's law is then only restrictive, directive, conservative, or destructive of something already created. I propose, then, to seek for the originative laws by which these subjects are furnished; in other word., for the causes of the origin of the fittest." 1 Mr. Cope lays great stress on the existence of a special <levelopmental force termed "bathmism" or growth-force, which acts by means of retardation and acceleration "without any reference to fitness at all;" that "instead of being controlled by fitness it is the controller of fitness." He argues that" all the characteristics of generalised groups from genera up (ex- cepting, perhaps, families) have been evolved under the law of acceleration and retardation," combined with some intervention of natural selection ; and that specific characters, or species, have been evolved by natuml selection with some assistance from the hio·her law. He, therefore, makes . pecies and genera two absolutely distinct thing., the latter not developed out of the former; generic characters and specific characters arc, in his opinion, fundamentally different, and have had different origins, and whole groups of species have been simultaneously modified, so as to belong to another genus ; whence he thinks it "highly probable that the same specific form has existed through a succession of genera, and perhaps in different epochs of geologic time." Useful characters, he concludes, have been produced by the special location of growth-force by use; useless ones have been produced by location of growth-force without the influence of use. Another element which determines the direction of growth-force, and which precedes use, is effort; and "it is thought that effort becomes incorporated into the metaphysical acquisitions of the parent, and is inherited with other metaphysical qualities by the young, which, during the period of growth, is much more susceptible to modifying influences, and is likely to exhibit structural change in consequence." 2 From these few examples of their teachings, it is clear that 1 Origin of the Fittest, p. 174.. 2 lbid. p. 29. It may be here noted that Darwin found these theories tmint lligible. In a Jetter to Professor E. T. Morse in 1877, he writes: ~'There is one point which I regret you did not make clear iu your Ad· |