SCIENCE. 



[N. S. Vol. XIX. No. 493. 



certainty that this hasty review will put 

 emphasis where subordination or oblivion 

 is better, and will notice slightly or not 

 at all researches which will loom up in the 

 future. Many titles which the speaker 

 thinks important have been left out from 

 lack of space and time. 



If ecology has a place at all in modern 

 biology, certainly one of its great tasks is 

 to unravel the mysteries of adaptation. 

 Are the many structures of animals and 

 plants, which are obviously of use, funda- 

 mental or accidental in an evolutionary 

 sense? The Darwinian and Lamarekian 

 theories, which have almost totally replaced 

 the gross teleology of former days, have 

 usually been supposed to imply an evolu- 

 tionary relation between an organ and its 

 use. The Lamarckians have emphasized 

 the direct response of organism to environ- 

 ment, and the inheritance of useful ac- 

 quired characters. The Darwinians have 

 emphasized the gradual 'working out' of 

 highly useful structures by the influence 

 of selection upon small fluctuating varia- 

 tions. The two theories are not necessarily 

 inharmonious; the Lamarckians have in- 

 quired more as to the origin of variations, 

 the Darwinians as to their survival. The 

 publication of DeVries's mutation theory 

 has occasioned a sharp change of front in 

 many c^uarters. We hear more now than 

 formerly of adaptation as a secondary 

 thing; that it has little or no significance 

 in an evolutionary sense. The idea that 

 an organ is not explained when we assign 

 it a function is not new; GeofEroy St. Hil- 

 aire made this one of the cardinal points 

 of his evolutionary philosophy nearly a 

 century ago, and we find the Greek philos- 

 ophers debating the question in their day. 



Professor Morgan's 'Evolution and 

 Adaptation' has called the adaptation 

 question once more to the fore. Morgan 

 holds that the mutation theory accounts 

 best for incipient organs, now useless, but 



eventually to become useful when fully 

 developed, for organs that are wholly use- 

 less, and for 'over-adapted' organs (such 

 as electric organs in fishes, leaf movements 

 of Desmodium gyrans). Many organs that 

 are useless or even harmful may survive 

 because the organism may have some com- 

 pensatory advantages making it as a whole 

 well adapted. Another whose work tends 

 to entice us from our former idols is Klebs, 

 whose ' Willkiirliche Entwicklungsander- 

 ungen' is certainly one of the great con- 

 tributions of the year. Klebs is removed 

 as far as possible from teleological ideas, 

 and explicitly states that they have ruled 

 so long because they are easy and restful 

 ways of solving life's riddles. He holds 

 that the poljanorphism of a plant, like that 

 of sulphur, is due to external agents, and 

 that -we should not ask for the purpose of 

 the changes in one case more than in the 

 other. The view just outlined is supported 

 by facts from various sources; MacDougal 

 has shown that etiolation is not, properly 

 speaking, an adaptation to the dark; that 

 plants are not to be looked upon as making 

 efforts to reach the light. Etiolation is a 

 response to certain factors, and may or 

 may not be useful. Willis in his studies 

 on the Podostemacese finds floral dorsiven- 

 trality, i. e., zygomorphy, keeping pace in 

 its development with increasing dorsiven- 

 trality in the vegetative organs. Zygo- 

 morphy here — so far from being an adapta- 

 tion to insects — characterizes flowers that 

 are in no sense entomophilous ; the only 

 entomophilous flowers of the group are the 

 more primitive actinomoriihic forms. If 

 natural selection does not operate her.e, 

 AVillis asks, why may not other cases of 

 zygomorphy be explained apart from in- 

 sect visitation? Kiister's 'Pathological 

 Plant Anatomy' also helps to strengthen 

 the chemico-physical view point of plant 

 structures, in that he treats as alike the 

 result of external agents, harmful struc- 



