BY THE GENERAL SURFACE OP THE SKIN. 205 



anterior extremity of the body, where the cei'ebral 

 ganglia lie, which is affected by light, and he suggests 

 that the light may pass through the skin and acts 

 directly on tlie nervous centres. 



Lacaze-Duthiers, Haeckel, Engelmann, Graber, 

 Plateau, and other naturalists have abundantly proved 

 the sensitiveness to light of other eyeless animals. 



There has, indeed, long been a vague idea that blind 

 people have some faint perception of light through the 

 general surface of the skin. So far as I am aware 

 there is not the slightest evidence or foundation for this 

 belief; nor, indeed, has it been advocated by any com- 

 petent authority. It seems a priori improbable that 

 an animal with complex eyes should still retain a 

 power which would be almost entirely useless. 



On the other hand, it is unquestionable that light 

 can, and often dues, act directly on the nerve termi- 

 nations without the intermediate operation of any 

 optical-apparatus. 



Some of them might, perhaps, be open to criticism. 

 The effect of heat may not have been always sufficiently 

 guarded against. Again, it is quite true that, as Plateau 

 observes " Lorsque les Myriapudes chilopodes aveugles 

 ou munis d'yeux, deposes sur le sol, s'introduisent avec 

 empressement dans la premiere fente qu'ils rencon- 

 trent, cet acte n'est pas determine par le seul besoin de 

 fuir la lumiere, ces animaux cherchent en memo temps 

 un milieu huuiide et avec lequel la plus grande paitie 

 de la surface de leur corps soit en contact direct." * 

 But though this is no doubt true, and though, perhaps, 

 the moisture may be some help, still, whatever be their 



* Plateau, " Rech. sur la perception de la lumiere par les Myriapodes 

 aveugles," Jov,r. de V Anatomie, etc., T. xxii. 1886. 



