282 PEEVIOUS OBSERVATIONS. 



a ci'ow. " To deceive this suspicious bird, the plan was 

 hit upon of sending two men to the watch-house, one 

 of whom passed on, while the other remained ; but the 

 crow counted, and kept her distance. The next day 

 three went, and again she perceived that only two 

 retired. In fine, it was found necessary to send five or 

 six men to the watch-house to put her out in her 

 calculation. The crow, thinking that this number of 

 men had passed by, lost no time in returning." From 

 this he inferred that crows could count up to four. 

 Lichtenberg mentions a nightingale which was said to 

 count up to three. Every day he gave it three meal- 

 worms, one at a time ; when it had finished one it 

 returned for another, but after the third it knew that 

 the feast was over. I do not find that any of the recent 

 works on the intelligence of animals, either Buchner, 

 or Peitz, or Romanes in either of his books, give any 

 additional evidence on this part of the subject. There 

 are, however, various scattered notices. 



According to my bird-nesting recollections, which I 

 have refreshed by more recent experience, if a nest 

 contains four eggs, one may safely be taken ; but if 

 two are removed, the bird generally deserts. Here, then, 

 it would seem as if we had some reason for supposing 

 that there is sufficient intelligence to distinguish three 

 from four. 



An interesting consideration rises also with refer- 

 ence to the number of the victims allotted to each 

 cell by the solitary wasps. Ammophila considers one 

 large caterpillar of iVbc<M« segetum enough; one species 

 of Eumenes supplies its young with five victims; 

 one ten, another fifteen, and one even as many as 

 twenty-four. The number is said to be constant in 



