MODERN BIOLOGY 605 



Speculations upon the main problems of life; he elaborated a theory of his 

 own that he called "conditionism," which was to replace the old ideas of 

 cause and effect by a conception of all phenomena's being due to a multi- 

 plicity of simultaneous conditions; what he was trying to get at was, of 

 course, the old contrast of things and phenomena and thereby ultimately 

 the contrast between the physical and the psychical, which he would replace 

 by an all-comprehensive "psycho-monism." But Verworn was no clear- 

 sighted thinker; conditionism is reminiscent of Mach's phenomenalism, 

 which, however, is far better thought out, and psycho-monism merely leads 

 to a great many far-fetched and unnatural attempts to get away from the 

 actually existing and observed difference between animate and inanimate, in 

 which the hypothetical "living" albumen must play the part of a universal 

 remedy for all difficulties. Through his enthusiasm, his brilliant style, and 

 his undeniably valuable contributions to the problem of the cell as a physi- 

 ological unit of life, Verworn has at any rate been an important personality 

 among the biologists of his age. 



Loeh on the movements of animals 

 A MECHANISTIC explanation of nature on entirely different grounds has been 

 produced by the experimentalist Loeb, who has been mentioned in the pre- 

 vious chapter. He was, as already pointed out, a pupil of Sachs, whose 

 studies of the tropisms of plants became the basis of his entire conception 

 of life. In his earlier years he himself carried out a number of valuable in- 

 vestigations on the subject of tropisms in the lower animals; since then he 

 has made the above-described experiments on parthenogenesis in eggs caused 

 by chemical reagents. The general theory of life that he set up is actually 

 based on these two classes of experiments. He regards, as far as is possible, 

 the movements of animals as tropisms caused by external influence; when an 

 animal moves towards the light, there actually takes place through the effect 

 of the light an oxidization of certain elements in the animal, and this causes 

 the movement; other movements, again, are induced by chemical associa- 

 tions that arise directly in the innermost being of the animal, as, for instance, 

 in the mating-flight of insects. On these facts he bases a "mechanistic con- 

 ception of life," which, however, he hardly succeeds in formulating in a 

 very convincing way. Indeed, he has no idea of a scientific student's duty 

 of first thinking out his theories; when his theory suits one case, it is at 

 once made to hold good for all cases without further investigation, and if 

 it does not do so, then the inexpedient cases are simply passed over. He gives 

 an account, for instance, of the phototropism of the Aphida:, on which he 

 carried out most ingenious experiments, and he traces the phenomenon to 

 the said oxidizing process — the fact that this phenomenon upon repeti- 

 tion proceeds with greater rapidity "may be brought about by" the lactic 

 acid produced by the muscles upon movement. Thus the phenomenon in 



