EECOGNITION AFTER A YEAR AND NINE ]\IONTHS. 230 



case five specimens of Lasius niger fell into water and 

 remained immersed for three hours. I then took them 

 out and put them into a bottle to recover themselves. 

 The following morning I allowed them to return. 

 They were received as friends, and, though we watched 

 them from 7.30 till 1.30 every hour, there was not the 

 slightest sign of hostility. The nest was, moreover, 

 placed in a closed box, so that if any ant were killed 

 we could inevitably find the body, and no ant died. 

 In this case, therefore, it is clear that the immersion 

 did not prevent them from being recognized. Again, 

 three specimens of Formica fusca dropped into water. 

 After three hours I took them out, and, after keeping 

 them by themselves for the night to recover, I put 

 them back into the nest. They were unquestionably 

 received as friends, without the slightest sign of 

 hostility or even of doubt. I do not, however, by any 

 means intend to express the opinion that smell is not 

 the mode by which recognition is effected. 



It will be remembered, perhaps, that my ants {For- 

 mica fusca) recognized one another after a separation 

 of a year and nine months, though '^ after some months' 

 separation they were occasionally attacked, as some of 

 the ants, perhaps the young ones, did not recognize 

 them. Still, they were never killed or driven out of 

 the nest, so that evidently when a mistake was made 

 it v>^as soon discovered." Hence it would appear that 

 there are differences in the memory of different 

 species. 



In one case Forel liad taken some ants from a 

 large nest of Comjoonotus, for the experiments on 

 their sensibility to the ultra-violet rays, to which I 

 have alreadv referred. After his observations were 



