74 STUDIES IN THE EVOLUTION OF ANIMALS 



the same origin, as the also temporary and irregular spots which 

 appear in other Fishes, as well as in several Tritons and many 

 Gekonides, without the interference of man. Some of the pro- 

 voked changes of colour do not entirely vanish after the irritation 

 is over, and they belong to the same category as the spots which 

 appear in many animals in youth and disappear with growing age. 

 Moreover, it is maintained that a series of slow gradations may be 

 established between the irregular spots, the spots arranged in rays, 

 and finally the stripes such as we see them in higher mammals 

 like the Zebra or the Tiger ; and if these generalisations prove to 

 be correct, we shall thus have an unbroken series from the tem- 

 porary spots provoked by light or electricity to the permanent 

 markings of animals.' 



I do not doubt that the pigments on the skins of animals are at 

 one end of the telegraphic wires (the nerves) which connect them 

 with the nerve-centres. Minute atomic changes, which, through age 

 and other causes, occur in the nerve-centres, influence electrically 

 the pigmentation of the skin ; but what we have to search for is why 

 all this is so. This investigation I have left for another place. 



Let us now study a little in detail the dapplings of the grey 

 Horse. 



In Fig. 36, at the joining of the shoulder and trunk, may be 

 seen several groups, consisting of a small roundish spot surrounded 

 by larger polygonal jag-edged spots, something like the enlarged 

 outlines shown in Fig. 42 (a). 



In Fig. 38 (lower Horse) similar groups of maculations can be 

 made out on the Horse's flank just behind the shoulder. Then in 

 Fig. 34 there are three well-marked similar groups placed in a line 

 slanting towards the abdomen, as well as several others. 



In Fig. 42 (b) I have given two Jaguar rosettes for comparison. 

 Those of (a) and of (fr) are very similar ; but I shall show in another 



