The Higher Usefulness of Science 71 



known of succeeding 1 stages, is familiar to every biolo- 

 gist. But that the student would be quite helpless with 

 the developing organisms were it not for his knowledge 

 of what they are to become, seems not to be sufficiently 

 noticed. That such antecedent knowledge is essential, 

 is manifest from the many cases in zoology where larvae 

 which undergo radical metamorphosis were discovered 

 before the adults of the same species were known, or at 

 any rate before the larvae were known to be the young 

 of the particular species. What has usually happened 

 in these cases is that either no attempt was originally 

 made to tell what the adult would be, and so to deter- 

 mine the taxonomic position of the larva; or an en- 

 tirely wrong guess as to its true nature and affinities 

 was made. The point is unequivocal once one reflects 

 on it. There are absolutely no observable attributes 

 in the germinal elements of any organism or even in 

 the advanced larvae of many (when these are regarded 

 by themselves) on which predictions can be based of 

 what they will develop into, just as there is nothing 

 observable about oxygen and hydrogen taken sepa- 

 rately that forecasts water, or about copper and 

 aluminum and manganese that forecasts magnetism in 

 Heusler's alloy. 



Shift now the point of view to phylogenesis and see 

 how the principle works there. The origin of new 

 kinds of plants and animals by mutation, about which 

 so much has been learned in late years, brings out the 

 point. What botanist or zoologist would pretend that 



