24 THE POPULAR SCIENCE MONTHLY. 



tliem. The minds of zoologists were not prepared in his time to 

 receive his ideas, and he had not the happy faculty of hitting 

 upon that clear and precise method of statement that imposes 

 itself and makes itself accepted by all. For a reformer to secure 

 a following, his idea should be defined with dazzling clearness 

 and precision, and achieve mastery by virtue of its seductive 

 force. Darwin's exposition of the universal and constant strug- 

 gle for existence, ending in the selection and survival of the vic- 

 tor, was so true and clear as to lead all readers into accord with 

 it. Cuvier, they said, could reconstruct the whole of an extinct 

 animal from a single bone. The thought spoke to the imagination 

 of the masses ; and when he laid down the principle that in an 

 organism, as in an equation, the known terms may be made to give 

 an unknown one, he commanded the admiration of a whole gen- 

 eration. Linnseus, who at a stroke reached the reform science 

 was aspiring after, to rid itself of nonsense in nomenclature, and 

 who found names to fit the occasion, became the tyrant of natural 

 history. It was not possible for Lamarck to realize a similar 

 success ; and a comparison of his arguments with those which 

 Darwin brings in support of the doctrine of changes in the forms 

 of animals, and a reference to the epoch in which he wrote, will 

 show why his ideas had to wait for the revelations of the English 

 naturalist before they could be recovered from oblivion. 



In view of the surprising discoveries to which the continuous 

 study of the evolution of the lower animals has led, and of the 

 direction of zoology under the influence of transf ormism into new 

 ways, it is impossible not to recognize that experiment alone ful- 

 fills the requirements of the moment. It is only through experi- 

 ment that the great questions of natural philosophy can be an- 

 swered ; that the discussions raised by clashing convictions, haz- 

 ardous assertions, so-called philosophical doctrines, and venture- 

 some syntheses too often lacking substantial bases, can be justly 

 appreciated or solidly established. 



The citation of a few instances will illustrate this assertion. 

 Every one has noticed the gall-nuts on oak-trees, excrescent tumors 

 produced by parasitical insects the Cynips which lay their eggs 

 in the mother plant by the aid of a gimlet - shaped ovipositor. 

 The young insect finds within this swelling all that it needs to sup- 

 port life, and quietly in it reaches complete development ; and it 

 can easily be caught as it issues from its prison. Entomologists 

 have catalogued a large number of species and genera belonging 

 to the family. In doing thus, they have followed pure and de- 

 scriptive zoology, as it was in the times of Linnaeus and Cuvier. 

 Now, it has been found, after watching the evolution of these 

 parasites, that all the genera and species have to be revised. Thus, 

 for example, we find on the superficial roots of an oak-tree galls 



