Cockayne. — The Terms "Species'" and "Variety" in Botany. 73 



Flora (1864), a work in constant use by all investigators of the New 

 Zealand flora for a period of thirty-five years. Here (p. xxiv) a species 

 is described as " all the individual plants which resemble each other 

 sufficiently to make us conclude that they are all, or may have been 

 all, descended from a common plant. These individuals may often differ 

 from each other in many striking particulars, such as the colour of the 

 flower, size of the leaf, &c. ; but these particulars are such as experience 

 teaches us are liable to vary in the seedlings raised from one individual. 

 When a large number of the individuals of a species differ from the others 

 in any striking particular they constitute a variety. If the variety 

 generally conies true from seed it is often called a ' race.' A variety 

 can only be propagated by grafts, cuttings, bulbs, tubers, or any other 

 method which produces a new plant by the development of one or more 

 buds from the old one. A race may with care be propagated by seed, 

 although seedlings will always be liable, under certain circumstances, to lose 

 those particulars which distinguish it from the rest of the species. A real 

 species will always come true from seed." 



The above definitions of Bentham are clear enough, and show plainly that to 

 him the idtimate test of a species was its capacity for breeding true. Bentham 

 (I.e., pp. xxiv, xxv) also deals with " occasional or accidental anomalies " 

 peculiar to one or a few individuals, which may prevent the species being 

 " at once recognized by its technical characters." These " aberrations " he 

 divides into two classes — viz., those for which some general cause may be 

 assigned, and those of which the cause is tmknown. To the first class 

 belong changes due to various ecological factors, to use the modern term; 

 while the second class includes those variations which some would now 

 consider due to mutation, or to some factor acting on the embryo at an 

 early stage of its development. Hybrids fall into Bentham's first class of 

 " anomalies." 



Biologically, if not taxonomically, the conception of species changed 

 with the general acceptance of the doctrine of evolution, so that many con- 

 sidered them to be much less sharply defined than had up to that time 

 been believed, while in no few instances they were thought to be not yet 

 fully differentiated. According to Poulton, Sir E. Ray Lankester goes so 

 far as to declare that " the ' origin ' of species was really the abolition of 

 species, and zoologists should now be content to name, draw, and catalogue 

 forms " (Essays on Evolution, p» 62, 1908). Poulton himself considers that 

 the usual diagnostic method of considering as species sets of individuals 

 arranged according to certain characters fixed upon by the systematist, 

 in a series without marked breaks, is not a sufficient conclusion, and he 

 suggests that, in addition, the members of the group must interbreed 

 and be of common origin. Romanes (Darwin and after Darwin, vol. 2, 

 p. 231, 1895), after some discussion regarding the term "species," gives 

 the following definition : "'A group of individuals which, however many 

 characters they share with other individuals, agree in presenting one or 

 more characters of a peculiar and hereditary* kind with some certain degree 

 of distinctness." 



Coming now to Darwin himself we find these words (The Origin of 

 Species, ed. 6, p. 400) : " Hereafter we shall be compelled to acknowledge 

 that the only distinction between species and well-marked varieties is that 



* The italics are mine. 



