ADDRESS TO BRITISH ASSOCIATION. 263 



which subsists between the two evohitions, that of the race, and that of 

 the individual. Treviranus, no less distinctly than his great contem- 

 porary Lamarck, was well aware that the affinities of plants and 

 animals must be estimated according to their developmental value, and 

 consequently that classification must be founded on development ; but 

 it occurred to no one what the real link was between descent and 

 development ; nor was it, indeed, until several years after the publi- 

 cation of the Origin that Haeckel enunciated that ' biogenetic law ' 

 according to which the development of any individual organism is but 

 a memory, a recapitulation by the individual of the development of the 

 race — of the process for which Fritz Miiller had coined the excellent 

 word ' phylogenesis ' ; and that each stage of the former is but a 

 transitory reappearance of a bygone epoch in its ancestral history. If, 

 therefore, we are right in regarding ontogenesis as dependent on 

 phylogenesis, the origin of the former must correspond with that of the 

 latter ; that is, on the power which the race or the organism at every 

 stage of its existence possesses of profiting by every condition or cir- 

 cumstance for its own adA^ancement." 



This being so, the importance of those views of entomology which 

 are sometimes termed speculative, but which are distinctly philosophical 

 in their bearing, is evident. How valuable, then, are the observations 

 made, not only on development as studied in the individual itself, in 

 its own organisation as it were, but also those made upon its develop- 

 mental changes when considered in relation to its environment. 

 How valuable, also, are all observations made on the variation of 

 individuals according to the differences of their environment ! Eacial 

 variation, now existent in a species, points to something deeper than 

 the mere superficial difference between the various races ; and the 

 plastic condition of some species, compared with closely allied species 

 which are remarkable for their constancy in the same genus, often 

 gives us a clue to the form (in a species) or the species (in a genus) 

 which possesses in the most marked degree the power of " profiting by 

 every condition or circumstance for its own advancement." 



The doctor then points out that " biology naturally falls into three 

 •divisions," and states that " these are even more sharply distinguished 

 by their methods than by their subjects : namely. Physiology, of which 

 the methods are entirely experimental ; Morphology, the science which 

 deals with the forms and structure of plants and animals, and of which 

 it may be said that the body is anatomy, the soul, development ; and, 

 finally, (Ecology, which uses all the knowledge it can obtain from the 

 other two, but chiefly rests on the exploration of the endless varied 

 phenomena of animal and plant life as they manifest themselves under 

 natural conditions. This last branch of biology — the science which 

 concerns itself with the external relations of plants and animals to each 

 other, and to the past and present conditions of their existence — is by 

 far the most attractive. In it, those qualities of mind which especially 

 distinguish the naturalist find their highest exercise, and it represents 

 more than any other branch, of the subject, what Treviranus termed the 

 ^ philosophy of living nature.' Notwithstanding the very general 

 interest which several of its problems excite at the present moment, I 

 do not propose to discuss any of them, but rather to limit mj^self to the 

 humbler task of showing that the fundamental idea which finds one 

 form of expression in the world of living beings regarded as a whole — 



