(size ) 
applied immediately after pupation ; while repeated experiments 
with the variety bryoniw gave no sufficient support to Weis- 
mann’s view (see above, p. 9) that this variety was the 
original parent-form of napi. 
It isin this memoir that Weismann first recognises fully 
what he had formerly questioned, but had latterly* put forward 
as probable, viz., that, besides the direct seasonal dimorph- 
ism attributable to temperature, there also exists adaptive 
seasonal dimorphism dependent on the indirect influence of 
the varying environment according to the time of year. He 
again cites the case of A. /evana itself as possibly exhibiting 
in its prorsa-form mimicry of Limenitis, and suggests that the 
seasonal forms of P. napi may be adapted on the underside to 
the vegetation tints of spring and summer respectively. In 
the case of the latter species he expresses the belief that 
adaptive and direct seasonal dimorphism are combined, point- 
ing out that the differences presented by the upperside may 
perhaps be referred to the direct influence of temperature. 
The possible adaptation of the green-and-white underside of 
the dimorphic Anthocharis belia to the respective resting 
-plants of each season is also indicated. 
The poverty, however, of such instances among the season- 
ally dimorphic species of the European butterfly-fauna is 
manifest ; and itis thus satisfactory to find Weismann turn- 
ing, in support of his view, to the numerous striking cases 
(first brought to his notice in 1894 in a paper by Dr. G, 
Brandes) of seasonal dimorphism occurring in tropical and 
sub-tropical regions, among which were instances where one 
seasonal form at least assumes a special protective colouring. 
Hitherto all the cases investigated and experimented on, 
whether in Europe or North America, had been found refer- 
able to the influence of high and low temperatures, and 
nobody seems to have suspected the occurrence of similar 
seasonal variation in hot countries; but, as Mr. L. de 
Nicéville, Mr. W. Doherty, and other observers have pointed 
out, and as Weismann was apt to recognise, the alternation of 
wet and dry seasons is as actively inciting an agent in the 
* «© Aeussere Einfliisse als Entwickelungsreize,” 1894. 
