SEASONAL POLYMORPHISM. 133 



conceive the other grades, apart from these extreme ones, as all having 

 the same hereditary tendencies and the races as produced simply by the 

 effect of environment on the development of each individual, although 

 experimental breedingof 6r//o«m^', of Rimiicia iihlaeax, and other species, 

 have shown that some characters have a tendency to persist in one or 

 two generations, notwithstanding altered surroundings. Grade VIIa I 

 call the interesting race from North Africa, which I have named maura 

 in Pihop. Pal. It shows no signs of being frail, like jiaeudorapae. Its 

 features consist in a combination of characters of the first generation 

 with characters of the second, such as I have never seen in Europe even 

 in single individuals. The upperside in characteristic specimens of both 

 sexes is absolutely that of the second generation of southern Europe; 

 the underside however is similar to that of the r/(///fl//.s individuals with 

 the thinnest nervural streaks ; they are sharply outlined and in no way 

 shaded and partly obliterated, as in pseudorajiae. Some males have the 

 apical crescent above broken up into streaks, as in some vuU^aris, but a 

 very large discal spot distinguishes them from any European specimen 

 of this generation. Some females have more basal shading and nervu- 

 ral streaks above than my " type " figured on pi. lix. I possess speci- 

 mens from La Calle (Alger), collected in February. As vuh/aris is also 

 found in Algeria, there remains to make out how these two perfectly 

 distinct forms, and presumably races, stand to each other in Africa. 

 It is quite remarkable that this should be the only case in which the 

 first generation shows signs of transition to the following; as a rule, 

 they are sharply distinct or (in the north of Europe) it is the second 

 generation which approaches the first. Evidently the very special 

 climatic conditions of northern Africa are the cause of this former 

 phenomenon. Some individuals of the Syrian psetulorajiae (see my fig. 

 24) recall maura by the shape of the wings and upperside markings 

 pointing to summer characteristics. 



Grades in the extent of the dark pattern, taken on the whole, and 

 races of P. napi, L., in Europe, detectable in the second and third 

 generation : — 



These generations do not produce such striking individual variations 

 as the first, so that much fewer forms have been named and races have 

 scarcely been noted. A comparison of series from the various regions 

 shows, on tne contrary, that geographical variation is quite consider- 

 able, as well as distinctive features between these two broods in each 

 locality, so that it is well worth working them out accurately. The 

 incredibly indiscriminate use which has been made of the name of 

 napaeae, Esper, as I shall presently point out, is no doubt partly 

 responsible for the neglect of this interesting group of forms, because 

 collectors and authors set their minds at ease by applying it to the one 

 that each of them chanced to find in his region ; in every local list we 

 invariably find napaeae and nothing more interesting than this. 



In a general way the features of these generations, as compared 

 with the first, may be said to consist in a broadening of the wings, 

 more convex outer margin, and in a tendency to obliteration of the 

 nervural pattern, which, as a rule, is, in most cases, except the northern 

 ones, entirely absent on the upperside, and in an increase of the true or 

 transverse pattern. The latter does not consist so much in an increase 

 of its extent, as in its becoming of a darker tinge and acquiring sharper 



