206 
DARWINISM 
CHA1>. 
those feeding on particular species of plants would rapidly 
acquire the peculiar tints and markings best adapted to 
conceal them upon those plants. Then, every little variation 
that, once in a hundred years perhaps, led to the preservation 
of some larva which was thereby rather better concealed than 
its fellows, would form the starting-point of a further 
development, leading ultimately to that perfection of imitation 
in details which now astonishes us. The researches of Dr. 
Weissmann illustrate this progressive adaptation. The very 
young larvae of several species are green or yellowish without 
any markings ; they then, in subsequent moults, obtain certain 
markings, some of which are often lost again before the larva 
is fully grown. The early stages of those species which, 
like elephant hawk-moths (Chserocampa), have the anterior 
segments elongated and retractile, with large eye-like spots 
to imitate the head of a vertebrate, are at first like those of 
non-retractile species, the anterior segments being as large as 
the rest. After the first moult they become smaller, com¬ 
paratively ; but it is only after the second moult that the 
ocelli begin to appear, and these are not fully defined till after 
the third moult. This progressive development of the in¬ 
dividual—the ontogeny—gives us a clue to the ancestral 
development of the whole race—the phylogeny; and ive are 
enabled to picture to ourselves the very slow and gradual 
steps by which the existing perfect adaptation has been 
brought about. In many larvae great variability still exists, 
and in some there are two or more distinctly-coloured forms 
— usually a dark and a light or a brown and a green form. 
The larva of the humming-bird hawk-moth (Macroglossa 
stellatarum) varies in this manner, and Dr. Weissmann raised 
five varieties from a batch of eggs from one moth. It feeds 
on species of bedstraw (Galium verum and G. mollugo), and 
as the green forms are less abundant than the brown, it has 
probably undergone some recent change of food-pi ant or 
of habits which renders brown the more protective colour. 
Special Protective Colouring of Butterflies. 
We will now consider a few cases of special protective 
colouring in the perfect butterfly or moth. Mr. Mansel 
Weale states that in South Africa there is a great prevalence 
