268 THE HUMAN SPECIES 



insignificant opening of its nest in the ground if it had not an 

 inner presentation of it : but the most incomprehensible point 

 to me is how Tiirkheim can deny that a bird has an inner 

 presentation of its nest and young. He argues in proof of the 

 impossibility of a dog forming a presentation of his master 

 that the dog cannot note all the details of the head, face, etc., 

 because he lacks the fundamental notions of light and dark, right 

 and left. As if these were essential, for the dog only needs to 

 recall a general impression. It is equally unfortunate to assert 

 that pictures, or plastic representations, evoke no ideas in 

 animals. One may see in any zoological garden how a monkey 

 looking in a mirror will make grimaces at his supposed com- 

 panion, and at last will stretch behind the glass to lay hold on him. 



As to denying the faculty of association to animals I will 

 only point to the example of the horse, that at the sight of the 

 smithy where it is to be shod, hangs back in its paces, not on 

 account of the smithy as such, but because it connects the sight 

 of the smithy with the idea of the clumsy blacksmith who had 

 previously mishandled it. 



Memory. As the result of his under-estimation of the 

 animal-mind Tiirkheim even denies that animals have memory, 

 without realising that memory is essential to the further evolu- 

 tion of the mind-life present in the unicellular Protista. Just 

 as in the lowest classes of Protista unconscious presentations are 

 to be found, so these may be reproduced by what may be 

 called unconscious memory, which may be called into play 

 again, for instance, in the Radiolaria and Thalamophorae, in 

 order to account for the retention of the fixed plan of their 

 skeletal structure. Ewald Hering, in 1870, summed up the 

 importance of memory to the organic world in these words : 

 " Memory is a function of organised matter, to which we owe 

 almost all we are and have " ; and the credit belongs to Haeckel 

 of having in 1876, in his work on the Perigenesis of the Plasti- 

 dule, investigated the functions of the plastidule, i.e., the 

 hypothetical molecule, or groups of molecules (perhaps the 

 cell-nuclei), which demonstrated the transmissibility of memory,, 

 and from this followed the whole existence of heredity, or as 

 Haeckel expresses it, " Heredity is the memory of the plasti- 

 dule ". 



