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sp which protects it。 Without processes of selection we should be obliged to assume a 〃pre…established harmony〃 after the famous Leibnitzian model； by means of which the clock of the evolution of organisms is so regulated as to strike in exact synchronism with that of the history of the earth！ All forms of life are strictly adapted to the conditions of their life； and can persist under these conditions alone。
There must therefore be an intrinsic connection between the conditions and the structural adaptations of the organism； and； SINCE THE CONDITIONS OF LIFE CANNOT BE DETERMINED BY THE ANIMAL ITSELF； THE ADAPTATIONS MUST BE CALLED FORTH BY THE CONDITIONS。
The selection theory teaches us how this is conceivable； since it enables us to understand that there is a continual production of what is non… purposive as well as of what is purposive； but the purposive alone survives； while the non…purposive perishes in the very act of arising。 This is the old wisdom taught long ago by Empedocles。
II。 THE LAMARCKIAN PRINCIPLE。
Lamarck； as is well known； formulated a definite theory of evolution at the beginning of the nineteenth century； exactly fifty years before the Darwin… Wallace principle of selection was given to the world。 This brilliant investigator also endeavoured to support his theory by demonstrating forces which might have brought about the transformations of the organic world in the course of the ages。 In addition to other factors； he laid special emphasis on the increased or diminished use of the parts of the body； assuming that the strengthening or weakening which takes place from this cause during the individual life； could be handed on to the offspring； and thus intensified and raised to the rank of a specific character。 Darwin also regarded this LAMARCKIAN PRINCIPLE； as it is now generally called； as a factor in evolution； but he was not fully convinced of the transmissibility of acquired characters。
As I have here to deal only with the theory of selection； I need not discuss the Lamarckian hypothesis； but I must express my opinion that there is room for much doubt as to the cooperation of this principle in evolution。 Not only is it difficult to imagine how the transmission of functional modifications could take place； but； up to the present time； notwithstanding the endeavours of many excellent investigators； not a single actual proof of such inheritance has been brought forward。 Semon's experiments on plants are； according to the botanist Pfeffer； not to be relied on； and even the recent； beautiful experiments made by Dr Kammerer on salamanders； cannot； as I hope to show elsewhere； be regarded as proof； if only because they do not deal at all with functional modifications； that is； with modifications brought about by use； and it is to these ALONE that the Lamarckian principle refers。
III。 OBJECTIONS TO THE THEORY OF SELECTION。
（a） Saltatory evolution。
The Darwinian doctrine of evolution depends essentially on THE CUMULATIVE AUGMENTATION of minute variations in the direction of utility。 But can such minute variations； which are undoubtedly continually appearing among the individuals of the same species； possess any selection…value； can they determine which individuals are to survive； and which are to succumb； can they be increased by natural selection till they attain to the highest development of a purposive variation？
To many this seems so improbable that they have urged a theory of evolution by leaps from species to species。 Kolliker； in 1872； compared the evolution of species with the processes which we can observe in the individual life in cases of alternation of generations。 But a polyp only gives rise to a medusa because it has itself arisen from one； and there can be no question of a medusa ever having arisen suddenly and de novo from a polyp…bud； if only because both forms are adapted in their structure as a whole； and in every detail to the conditions of their life。 A sudden origin； in a natural way； of numerous adaptations is inconceivable。 Even the degeneration of a medusoid from a free…swimming animal to a mere brood… sac （gonophore） is not sudden and saltatory； but occurs by imperceptible modifications throughout hundreds of years； as we can learn from the numerous stages of the process of degeneration persisting at the same time in different species。
If； then； the degeneration to a simple brood…sac takes place only by very slow transitions； each stage of which may last for centuries； how could the much more complex ASCENDING evolution possibly have taken place by sudden leaps？ I regard this argument as capable of further extension； for wherever in nature we come upon degeneration； it is taking place by minute steps and with a slowness that makes it not directly perceptible； and I believe that this in itself justifies us in concluding that THE SAME MUST BE TRUE OF ASCENDING evolution。 But in the latter case the goal can seldom be distinctly recognised while in cases of degeneration the starting…point of the process can often be inferred； because several nearly related species may represent different stages。
In recent years Bateson in particular has championed the idea of saltatory； or so…called discontinuous evolution； and has collected a number of cases in which more or less marked variations have suddenly appeared。 These are taken for the most part from among domesticated animals which have been bred and crossed for a long time； and it is hardly to be wondered at that their much mixed and much influenced germ…plasm should； under certain conditions； give rise to remarkable phenomena； often indeed producing forms which are strongly suggestive of monstrosities； and which would undoubtedly not survive in free nature； unprotected by man。 I should regard such cases as due to an intensified germinal selectionthough this is to anticipate a littleand from this point of view it cannot be denied that they have a special interest。 But they seem to me to have no significance as far as the transformation of species is concerned； if only because of the extreme rarity of their occurrence。
There are； however； many variations which have appeared in a sudden and saltatory manner； and some of these Darwin pointed out and discussed in detail： the copper beech； the weeping trees； the oak with 〃fern…like leaves；〃 certain garden…flowers； etc。 But none of them have persisted in free nature； or evolved into permanent types。
On the other hand； wherever enduring types have arisen； we find traces of a gradual origin by successive stages； even if； at first sight； their origin may appear to have been sudden。 This is the case with SEASONAL DIMORPHISM； the first known cases of which exhibited marked differences between the two generations； the winter and the summer brood。 Take for instance the much discussed and studied form Vanessa （Araschnia） levana…prorsa。 Here the differences between the two forms are so great and so apparently disconnected； that one might almost believe it to be a sudden mutation； were it not that old transition…stages can be called forth by particular temperatures； and we know other butterflies； as for instance our Garden Whites； in which the difference