44-8 Lieut.-Col. N. Manders on the Study of Mimicry by 



of individuals, the material out of which a good transitional 

 series between it and chrysippus could be constructed" 

 (" Essays on Evolution," p. 70). 



As to the factor which produced these intermediates, 

 Professor Poulton, in a letter to me, writes, "The species 

 (chrysippus) has a double constitution A and B, developed 

 from internal causes (viz. within itself, and hereditary), 

 but they are not so far crystallised out but what some 

 effect in the direction of A or B may be produced by 

 external causes ; but not apparently the whole effect — at 

 least so far as you have gone." And again, " I do not 

 change my view that the ultimate cause is internal and 

 not external. That the internal condition can be modified 

 to some extent your experiments certainly seem to show: 

 although you do not produce the full dorippus effect, what- 

 ever you do. The full dorippus form is a dominant one 

 on Kilimanjaro, with all its mountain moisture, showing, 

 I think, that it is not heat and dryness that produce it. 

 The same conclusion is supported by the fact that dorippus 

 is extremely rare south of the Zambesi, although there are 

 vast tracts of land that are dry, hot, and desert, for a large 

 part of the year. Hence, although the germ-plasm seems 

 certainly alterable by heat, that does not seem to be the 

 way that usually works in nature. It may be so in the 

 desert area of Ceylon, accounting for the isolated indi- 

 viduals that occur there of dxyrvjppus. Inaria is even more 

 clearly independent of climatic causes, for its proportion 

 is considerable all over Africa ; yet the climate varies 

 immensely. It is a common form on the West Coast." 



I quite agree that the cause is internal and hereditary, 

 but rather consider that the constitution is simple and 

 that an external cause such as shock to the developing 

 pupa throws it back to an earlier form of its internal 

 development. That external conditions have in them- 

 selves power to produce some effect is indicated by the 

 approach to the Sumatra form by the agency of moist 

 heat, and Mr. Merrifield has shown by his experiments on 

 Chrysophanus phloeas, that that butterfly is ready to assume 

 a different colouring according to the temperature at which 

 the larva is reared. But in the present state of our know- 

 ledge it is frequently impossible to say what is due to in- 

 ternal causes and what to the pressure of external conditions. 



The question arises which is the ancestral form, chriisipp>ios 

 or dorippus ? Most entomologists, I believe, consider the 



