PROGRESS 21 



experiments on the behaviour of crabs. The method 

 by which the sexes recognize each other is so crude 

 that I am not sure whether it deserves the term 

 recognition at all. Before mating, which takes 

 place immediately after a moult, the female is carried 

 about for some time in the claws of the male. The 

 mature males will attempt to lift up and carry off any 

 members of the same species, male or female : but 

 the only ones which will permit themselves to be thus 

 carried about are females j ust before moulting. Hence 

 by a general instinct to lift any members of the same 

 species on the part of the males, and on the part of the 

 females an instinct to allow themselves to be lifted 

 when in the physiological condition which precedes 

 moulting, the required end is brought about. But 

 of any mental operation such as is involved in sex- 

 recognition in man or any other mammal, there is no 

 evidence. 



Fish, to take another example, possess associative 

 memory ; they can learn. But they learn very slowly, 

 and learn only the simplest things. The jump from 

 their powers of memory to those of a dog, who can 

 be trained comparatively quickly to carry out com- 

 plicated tricks, is as great as the further jump from the 

 powers of a dog to those of a man capable of learning 

 a page of print by heart in two or three readings. 



The first organs connected with mind to become 

 elaborated are the organs of sense : but such receptor 

 organs are useless to their possessor, however elaborate. 



