192 Studies in Animal Behavior 



tion of such a very different creature as the but- 

 terfly. Here cells much like the leucocytes act as 

 devouring cells or phagocytes which engulf the ma- 

 terials of the degenerating tissues. 



Apparently the leucocytes are omnivorous in their 

 appetite. One of my former students, Dr. Fasten, 

 who has made a thorough study of the behavior 

 of these cells, finds that they engulf even such sub- 

 stances as sulphur and chrome yellow, which would 

 be rejected by an Amoeba or almost any other free 

 organism. This indiscriminate appetite would be 

 fatal to a creature living a free life. Probably it 

 is not particularly good for the leucocytes; but it 

 must be remembered that the role of these cells is 

 primarily altruistic. They work for the welfare of 

 the body physiological. They are reproduced not 

 so much from other leucocytes (although this proc- 

 ess occurs) as by the division of cells in bone mar- 

 row and certain other organs of the body. They 

 are meant for sacrifice after a life of service. And 

 Nature has made them rather more than usually 

 unmindful of their individual welfare. 



However these cells do show many of the pur- 

 posive reactions so commonly found in free organ- 

 isms. Dr. Fasten by a delicate apparatus has suc- 

 ceeded in bringing the point of a very fine glass 

 rod against one side of the cell. The leucocyte 

 thus irritated put out pseudopodia opposite the point 

 of the rod and crept away from the stimulus. The 

 method of response was practically the same as that 



