the Species as a Gene-complex. 113 



tlie varying degree to wliicli tlie cliaracters composing tlie 

 complex are represented in the individual (r/. 6, p. 263). It 

 seems, therefore, that a division of labour is desiiable. The 

 anatomist should indicate various types of charact'.'r- 

 association, and the experimentalist should analyse such cases 

 and assign to them a conect genetic interpretation. 



One can imagine that the result of such a study of 

 cliaracter-associations might yield one of the results suggested 

 above, viz., every degree of association from the most 

 unstable to the most complete li!d?:age. Would we in such a 

 case be any nearer our goal ? The "species" would still be 

 a concept only — a projection of our minds in their search for 

 a point d^appui in the perplexing multitude of types of 

 association. We would, however, have arrived at a clearer 

 conception of the way in which the associations originally 

 distinguished as "species" are built up, maintained, or dis- 

 sociated. We would concentrate less upon the association 

 itself than on the way it is represented in the individual. 



In practice we find it increasingly difficult, as animals are 

 subjected to a more intensive study, to make our rigid con- 

 cepts fit the facts of Nature. Not only species but genera 

 and families appear to be mere abstractions which form a sort 

 of " Bed of Procrustes ^' in which the affinities of animals 

 are often painfully distoi ted in order to fit the inelastic frame- 

 work. On the other hand, it is obvious that we cannot relapse 

 into apassive acceptance of an animal kingdom wholly anarchic 

 in the relationship of its units. The observations of com- 

 petent field-naturalists and taxonomists show us that some 

 associations at least are permanent. The fault of taxonomy 

 in the past seems to have been not that its units are unreal, 

 but that it has extended them unwarrantably. A well-known 

 case may make the above generalizations clearer. 



The two species of snail, Tachea hortensis ?^ndi T. nemoralis, 

 are widely distributed in West and Central Europe. They 

 have been the objects for many years of a solicitous 

 examination usually made in order to answer the questions : 

 *' Are they two species, and, if so, what is the real differ- 

 ence ? " 



These studies were originally conchological, but the imm- 

 ber of structures examined has been increased and breeding- 

 experiments have been conducted with the animals. One 

 of the chief results for our purpose is that places are known 

 where the pure hortensis shell-form is obtained either with or 

 without the pure nemorahs shell-form, and vice verad. On 



Ann. (& Mag. iV. Hist. Ser. 9. Vol. xi. 8 



