38 THE FOUNDATIONS OF ZOOLOGY 



is perhaps as well for those who are teachers to keep their faith 

 outside the laboratory as much as possible. 



With this qualification I have nothing but approval for the pas- 

 sage quoted, as well as for the rest of the essay. Like Huxley, I 

 hold that we are logically bound to apply to protoplasm the same 

 conceptions as those which are held to be legitimate elsewhere. 

 Without believing, I certainly see no reason for doubting that all 

 the properties of organisms may possibly be some day deduced from 

 the nature and disposition of their constituent molecules. If I 

 should live to see this proved, I should believe it without remodel- 

 ling any beliefs I now hold ; for most assuredly I do not believe 

 that these activities are the result of anything else than physical 

 structure. I simply do not know, and have no belief whatever on 

 the subject, although I welcome every addition to our knowledge 

 of the properties of the physical basis of life, in the conviction that 

 this knowledge is a necessary condition for progress. I must also 

 insist, however, that nothing seems more obvious to me than that 

 we might study the form of the parts of a watch, and the way they 

 are put together, till the crack of doom, without understanding it 

 in any sense worthy the name. To understand it we must study 

 not only its mechanism and the movements to be deduced from it, 

 but the movements of the earth as well ; and then we must study 

 a third thing, — that relation between the two which fits a watch for 

 man's service. I hold that, in this sense of the word, we can 

 "understand" watches, and that good common sense forces us to 

 admit not only that the fitness of a watch is real, but that it is the 

 only basis for rational interest in watches. Analogies are dangerous 

 weapons, because of our fondness for pushing them farther than 

 the facts warrant, and for assuming that resemblance in one feature 

 involves resemblance in other features. The fact that living things 

 are like watches in their fitness, in their adjustment to the phe- 

 nomena of the external world, at once suggests many interesting 

 questions with which I have no intention to deal at present. This 

 particular resemblance is obvious, and I hold that whatever may 

 be possible to the zoologist of future ages, the only method of study- 

 ing this fitness which is available at the present day is like that 

 which we apply to watches. 



Huxley says : " If the properties of water may be properly said 



