84 



over the whole of the upper side of the wings. This type, Bry- 

 otiicB, occurs in polar regions as the only form of Napi, and is also 

 found in the higher Alps, where it flies in secluded meadows as 

 the only form, but in other localities less isolated it is mixed with 

 the ordinary form of the species. In both regions Bryonies pro- 

 duces but one generation a year, and must then, according to my 

 theory, be regarded as the parent form of Napi.'' On page 44 ; 

 " In the Alps and Jura, the ordinary form of TVisr/z swarms every- 

 where from the plains towards the habitat of Bryonies, so that a 

 crossing of the two forms may occasionally or even frequently 

 take place ; and it is not astonishing if in some places, Meiringen 

 for example, a perfect series of intermediate forms between Napi 

 and Bryonies is met with. That crossing is the cause of the great 

 variability of Bryonia in the Alpine districts is proved by the 

 fact that in the Polar regions this form * is by no means so vari- 

 able as in the Alps, but judging by about 40 to 50 Norwegian 

 specimens, is rather constant. My friend, Dr. Staudinger, who 

 has twice spent the summer in Lapland, thus writes in reply to 

 my question. A crossing with Napi cannot there take place, as 

 this form is never met with, so that the ancient parent-form Bry- 

 onies has been able to preserve its original constancy." 



Dr. Weismann, page 40, relates how he obtained eggs from a 

 female Bryonne in June in a secluded Alpine valley, and sub- 

 jected the pupae therefrom to a high temperature in a hot-house, 

 but only one butterfly emerged the same summer, in spite of 

 this high temperature, and of what he regards as of more special 

 importance, in spite of the want of cooling at night, and that this 

 was a male Bryonies. " The other pupae hibernated in the 

 heated rooms, and produced from the end of January to the be- 

 ginning of June, 28 butterflies, all of which were exquisite Bry- 

 onies. Experiment thus confirmed the view \\idX Bryonies x's.th.^ 

 parent form of Napi, and the description hitherto given by system- 

 atists ought therefore properly to be reversed. Pieris Bryo7iies 

 should be elevated to the rank of a species, and the ordinary winter 

 and summer forms should be designated as vars. Napi and Napeses!' 



Boisduval describes Napi {i. e., the ordinary winter form) thus : 

 " Wings white, with the base a little ash-colored. Primaries have 

 the apex and ordinarily the extremities of the nervures black ; 

 the disk sovietinies without spots in the male, anei sometimes with 

 one black spot, as in Rapes ; in the female oreiinarily tzvo spots and 

 a black stripe situated as in the female of BrassiccB and of Rapes. 

 Secotidaries have a black spot on costal margin. Under side of 

 primaries white, with two black spots as in the allied species, the 

 apex yellow ; under side of secondaries of a pale yellow, with 

 veins of blackish-green covering the nervures." Westwood says: 

 " The males generally have a black spot between the middle and 

 apex of the wing (primaries) ; the females have two large black 

 spots towards the posterior margin, the hineler one being connected 



