PREFACE. IX 



great measure to the unfortunate circumstance that Natural History 

 lias come to be used as a vehicle for elementary education, a 

 purpose to which it is unsuited. From the conditions of the case 

 when very large classes are brought together it becomes necessary 

 that the instruction should be organized, scheduled, and reduced to 

 diagram and system. Facts are valued in proportion as they lend 

 themselves to such orderly treatment ; on the rest small store is 

 set. By this method the pupil learns to think our schemes of 

 Nature sufficient, turning for inspiration to books, and supposing 

 that by following his primer he may master it all. In a specimen 

 he sees what he has been told to see and no more, rarely learning 

 the habit of spontaneous observation, the one lesson that the 

 study of Natural History is best fitted to teach. 



Such a system reacts on the teacher. In time he comes to 

 forget that the caricature of Nature shewn to his pupils is like 

 no real thing. The perspective and atmosphere that belong to 

 live nature confuse him no more. Two cases may be given in 

 illustration. Few animals are dissected more often than the 

 Crayfish and the Cockroach. Each of these frequently presents 

 a striking departure from the normal (see Nos. 83 and 625) in 

 external characters, but these variations have been long unheeded 

 by pupil and by teacher; for though Desmarest and Brisout 

 published the facts so long ago as 1848, their observations failed 

 to get that visa of the text-books without which no fact can 

 travel far. 



It is especially strange that while few take much heed of the 

 modes of Variation or of the visible facts of Descent, every one is 

 interested in the causes of Variation and the nature of " Heredity,'" 

 a subject of extreme and peculiar difficulty. In the absence of 

 special knowledge these things are discussed with enthusiasm. 

 even by the public at large. 



But if we are to make way with this problem special know- 

 ledge is the first need. We must know what special evidence each 

 group of animals and plants can give, and this specialists alone 

 can tell us. It is therefore impossible for one person to make any 

 adequate gathering of the facts. If it is to be done it must be 

 done by many. At one time I thought that a number of persons 

 might perhaps be induced thus to combine ; but though I hope 

 hereafter some such organized collection may be made, it is 

 perhaps necessary that the first trial should be single-handed. 



