CHAP. XIX.] MORPHOLOGY. 229 



the law of adaptation, jointly with some other law of a 

 totally different and quite peculiar kind. 



The law of adaptation may be briefly stated thus : — Statement 

 Every organ is adapted, structurally and functionally, to o^*^^^*^^^- 

 all the rest ; and the whole organism, and every organ in 

 it, is adapted to its mode of life. This is true ; every fact 

 of organic morphology is consistent with it, subject to 

 some small though remarkable exceptions, of which I shall 

 have to speak further on : but it is not true, as we shall 

 find, that eveiy fact of morphology can be referred to 

 it alone. 



Crystalline morphology and organic morphology are so Crystallme 

 remote from each other, that no analogical reasoning from ^orpho- 

 the one to the other can be in the slightest degree conclu- logy- 

 sive. But such analogies may be very suggestive. We have 

 seen that crystals of the same species are subject to great 

 variations in form, due to chemical differences in the medium 

 from which they have been formed ; and that there is reason 

 to believe in similar variations among the lower species 

 of organisms, due to the soil, or medium, in which they 

 are developed. "We know that in crystals, notwithstanding 

 the variability of form within the limits of the same species, 

 there are definite and very peculiar formative laws, which Formative 

 cannot possibly depend on anything like organic functions, ci-TOtalli- 

 because crystals have no such functions ; and it ought not zation 

 to surprise us if there are similar formative, or morpho- pendent 

 logical, laws among organisms, which, like the formative °! f"'^*^- 

 laws of crystallization, cannot be referred to any relation 

 of form or structure to function. Especially, I think, is The same 

 this true of the lowest organisms, many of which show trae in 

 great beauty of form, of a kind that appears to be altogether part, of 

 due to symmetry of growth ; as (to mention the best in- f^"^ 

 stance that occurs to me) ^ the beautiful star-like rayed 



organic 

 rms. 



1 I quote the following instance of the same kind of beauty resulting 

 from regularity, from the Duke of Argyll's " Eeign of Law," pp. 199, 200 : 

 [The Diatomaceae, a group of the lowest Algfe,] "have shells of pure silex, 

 and these, each after its own kind, are all covered with the most elaborate 

 ornament — striated, or fluted, or punctured, or dotted, in patterns which 

 are mere patterns, but patterns of perfect, and sometimes of most complex 



