332 THE HISTORY AND SCOPE OF ZOOLOGY IX 



different kinds of as^reement in animal structures, 

 which, owinof to the want of such " counters of 

 thought," had been hitherto continually confused. 

 Analogous structures in any two animals compared 

 were by Owen defined as structures performing similar 

 functions, but not necessarily derived from the modi- 

 fication of one and the same part in the "plan" or 

 " archetype " according to which the two animals 

 compared were supposed to be constructed. Homo- 

 logous structures were such as, though greatly differ- 

 ing in appearance and detail from one another, and 

 though performing widely different functions, yet 

 were capable of being shown by adequate study of a 

 series of intermediate forms to be derived from one 

 and the same part or organ of the " plan-form " or 

 " archetype." It is not easy to exaggerate the service 

 rendered by Owen to the study of Zoology by the 

 introduction of this apparently small piece of verbal 

 mechanism ; it takes place with the classificatory 

 terms of Linnseus. And, though the conceptions of 

 *' archetypal Morphology," to which it had reference, 

 are now abandoned in favour of a genetic Morphology, 

 yet we should remember, in estimating the value of 

 this and of other speculations which have given place 

 to new views in the history of science, the words of 

 the great reformer himself. " Erroneous observations 

 are in the highest degree injurious to the progress of 

 science, since they often persist for a long time. But 

 erroneous theories, when they are supported by facts, 

 do little harm, since every one takes a healthy pleasure 

 in proving their falsity " (Darwin). Owen's definition 



