EXPERIMENTS IN HYBRIDIZATION AND TEMPERATURE. 165 



manipulation imagines were obtained from piippe of the summer 

 form from Zurich, which approached in a marked degree those 

 found in July and August in Syria and sometimes at Antioch 

 and Jerusalem. Further, the second generation of P. jwdaUriiis 

 from Wallis can be changed by warmth to the more characteristic 

 summer form of southern localities — that is, the typical var. 

 zanckeus, L., of Sicily, and so forth. 



3. Changes in the direction of sexual colour dimorphism. By 

 warmth the female of Parnassius apollo, L., from Wallis, was 

 entirely changed to the male type of coloration, and the male 

 had the dark spots on the outer margin of the fore wings replaced 

 by white. Sexual colour dimorphism must certainly only be 

 regarded as a link in the chain of the normal development of the 

 species, and in the case before us — as, indeed, it seems to be the 

 rule — the male is the newer type, and the female the older. 

 Therefore in our experiment the older female type was changed 

 to the newer male type, and the male evolved still further in a 

 progressive direction. 



It is also noteworthy that the dead whitish colour of the 

 female Rhodocera rhamni, L., is changed by warmth to the 

 intense yellow male coloration, either totally or partially. This 

 important change in the coloration of the female is not so much 

 a phylogenetic as a physiological matter, as is shown by the 

 correlation between the colour and the genital organs. In some 

 of these warmth experiments, and especially in the case before 

 us, certain female specimens underwent a certain amount of 

 damage and malformation to the sexual organs, and this mal- 

 formation seemed to be directly connected with the change of the 

 female colour. 



4. Phylogenetic forms* in their truer sense — that is, forms 

 which at present do not occur on the earth, or only very rarely. 



-■' In February, 1898, a large number of P. hospiton, Gene (pupae from 

 Sardinia), were made to approach P. macliaon in wing-outline and markings 

 by warmth. The fore wings were much more extended, the tail of the hind 

 wings lengthened, the j'ellow half-moon spots on the outer margins of the 

 upper sides of the fore and hind wings, and the red eye-spot at the anal 

 angle of the hind wings were noticeably increased in size, and in some 

 specimens yellow scales were sprinkled thickly on the black base of the fore 

 wings on the upper side, and on the broad black bands near the outer margin ; 

 all of these changes are approaches to the type of P. macliaon, L. PI. I. 

 fig. 1 shows a female specimen which shows tlie change in the shape of the 

 wing very plainly. 



It appears therefore as if P. hospiton, which, as is well known, inhabits 

 exclusively the mountain regions of Corsica and Sardinia, and whose claim 

 to the title of a separate species, as well as Argynnis elisa, God., and 

 Satyrus neomiris, God. (also species indigenous to Corsica and Sardinia), 

 are chiefly owing to its insular isolation, obtained certain changes in colour 

 and wing-structure, both with a correlative relationship to each other, from 

 the nearly related P. machaon, during some past epoch of low temperature. 

 It is a fact that P. hospiton is inclined to converge with P. machaon ja 

 several directions by a slight increase of temperature, 



