338 



SCIENTIFIC THOUGHT. 



place since the publication of Darwin's works, by the 

 industry of friend and foe, with the object of prov- 

 ing or of disproving and modifying Darwin's theories. 

 Whole chapters, such as those referring to the fer- 

 37. tilisation of plants through insects, to the part which 



Fertilisation 



of plants and colour plays in the world of flowers or in the plumage 



"Mimicry." 



of birds and in the wings of butterflies and moths, 

 have been added to our handbooks of natural history ; l 



1 Two remarkable instances may 

 be mentioned. It was known to 

 Christ. Conrad Sprengel that many 

 flowers are " dichogamous " i.e., 

 that though the organs for self- 

 fertilisation exist in the same flower, 

 nevertheless, because of a want of 

 timekeeping or for other reasons, 

 pollination is done by crossiug, 

 wherein the visits of insects are in- 

 strumental through elaborate exist- 

 ing arrangements. " Variously col- 

 oured spots serve as honey-guides 

 and pathfinders to the exploring 

 insects, hairs protect the nectar 

 from rain and yet offer no obstacle 

 to desirable visitors, other arrange- 

 ments secure that the insects are 

 dusted with pollen" (J. A. Thom- 

 son, 'The Science of Life,' p. 192). 

 Sprengel published his observations 

 in a remarkable book (1793) with 

 the title ' The Secret of Nature 

 discovered in the Structure and 

 Fertilisation of Flowers.' Such 

 was the enthusiasm of this true 

 naturalist, that he, " after being 

 ejected from the rectorate of Span- 

 dau for neglecting his flock in 

 favour of flowers, settled down to 

 a frugal life in Berlin, and gave 

 lessons in languages and botany. 

 The commonest plant became new 

 by what he had to say about it ; 

 a hair, a spot, gave him oppor- 

 tunity for questions, ideas, investi- 

 gations" (ibid., p. 191). Sachs 

 ('Gesch.,' p. 449) considers Spren- 

 gel's little work to contain "the 



first attempt to explain the genesis 

 of organic forms out of definite 

 relations to their environment." 

 For sixty years this biouomical 

 classic was forgotten. Darwin in 

 1841 heard of it through Robert 

 Brown, who, according to Dr Gray 

 ('Nature,' 1874, p. 80), "in com- 

 mon with the rest of the world, 

 looked on Sprengel's ideas as fan- 

 tastic." The book impressed Dar- 

 win, who in 1837 had written in 

 his notebook : " Do not plants 

 which have male and female organs 

 together, yet receive influence from 

 other plants ! " as being " full of 

 truth." (See ' Life of Darwin,' vol. 

 i. p. 90 ; vol. iii. p. 257.) The other 

 important research which has been 

 much stimulated by the two great 

 propounders of Darwinism, is the 

 study of the meaning of colours 

 in plants and animals and the allied 

 subject of "Mimicry." "It is 

 the wonderful individuality of the 

 colours of animals and plants that 

 attracts our attention the fact 

 that the colours are localised in 

 definite patterns, sometimes in 

 accordance with structural char- 

 acters, sometimes altogether in- 

 dependent of them, while often 

 differing in the most striking 

 and fantastic manner in allied 

 species. We are thus compelled to 

 look upon colour not merely as a 

 physical but also as a biological 

 characteristic, which has been dif- 

 ferentiated and specialised by 



