(498) 



of one (as in Precis). He will be able to come to a correct conclusion where 

 the systematist of the old school is quite heljiless. 



This helplessness has very aptly been characterised by Prof. E. B. Ponlton, 

 when speaking of the seasonal phases of Precis* : "The results [p. 458] which 

 have been described and illustrated in this section of the present memoir are so 

 startling that they may well shake the confidence of naturalists in the whole fabric 

 of insect systematics. If such forms as [Precis] iiataleiisis and sesamus, as simia 

 and avtilope, as pelasgis and archesia, are nothing but the generations of two 

 alternating phases of a single species, approximately synchronised with the heat 

 and cold or humidity and dryness of the alternating seasons, naturalists may feel 

 driven to ask, ' What becomes of the validity of sj)ecific distinctions ? ' . . . Under 

 the shock of Mr. Marshall's discovery that sesamus and mitalensis are two forms 

 of the same species, the systematist may well feel donbt.s about the foundations 

 npon which his science has been erected." ... [p. 49(i] " There is, however, 

 nothing revolutionary or subversive in any of these interesting facts. The 

 conventional marks of specific distinction remain just as they were, convenient 

 indications to the systematist, enabling bim ])rovisionally to separate groups of 

 individuals into assemblages we call species. When his work is done carefully 

 subsequent breeding experiments will, we may be sure, confirm his conclusions 

 in the majority of cases. But here and there startling exceptions will be found, 

 when it is to the advantage of a species to appear in two or more very different 

 forms." ... [p. 4G0] : " There is nothing subversive in the thought that certain 

 species exposed to different organic environments in two seasons of the year may 

 appear as cryjitic generations at one of these, aposematic or pseudaposematic at 

 the other. The explanation is at any rate sufficiently probable to enable us to 

 contemplate Mr. Marshall's wonderful discovery with equanimity and with an 

 interest undistnrbed by the thought that he has laid in ruins the whole edifice 

 of insect systematics." 



That is a low estimate of the results of systematic work, but a jnst one if 

 applied to those Lepidopterists who are guided by the rule : " conspicuous external 

 differences, two species ; no conspicuous external differences, one species." But if 

 the estimate is meant to imply that the results of research in systematics must 

 always remain as poor as those characterised, it is erroneous. The scope of 

 systematic work is not so limited as there represented. Certainly, we read 

 every now and again in works on Lepidoptera that the " sjjecies " of a certain 

 genus can only be ascertained by breeding. We see that intergraduate 

 sjiecimens between " species " are got rid of by putting them down as hybrids, 

 and that numerous forms are described as " var. ? " " ab. ? " " spec. dist. ? " 

 That this is so, is not the consequence of an inherent futility of systematics 

 as such, but is to a large extent the fault of the respective systematists 

 who did not employ the means at their disposal. If the authors interested 

 in African Butterflies had worked on them in the same way as, for instance, 

 Messrs. Godman and Salvin have done in the case of the Central American 

 Butterflies, and Messrs. Elwes and Edwards in the case of various groups of 

 Oriental and Holarctic Butterflies, the connection between the various supposed 

 " species " of Precis would not have remained a secret for so long. Seasonal and 

 non-seasonal dimorjjhism can easily be recognised by tiie examination of the 

 genital armature of the Butterflies — at least in all those cases where the species 



• Frans. Ent. Snc. Land. 11102. 



