Chap. II. THEIR INTELLiaENCB. 85 



division far oftener than on either of the two 

 other divisions. For the area of the basal to 

 the apical part is as 5 to 1, so that the 

 chance of the former being drawn into a 

 burrow by suction, will be as 5 to 1, compared 

 with the apical part. The base offers two 

 angles and the apex only one, so that the 

 former would have twice as good a chance 

 (independently of the size of the angles) of 

 being engulfed in a worm's mouth, as would 

 the apex. It should, however, be stated that 

 the apical angle is not often seized by worms ; 

 the margin at a little distance on either side 

 being preferred. I judge of this from having 

 found in 40 out of 46 cases in which tri- 

 angles had been drawn into burrows by their 

 apical ends, that the tip had been doubled 

 back within the burrow for a length of 

 between gV^^ ^^ ^^ ^^^^ ^^^ 1 inch. Lastly, 

 the proportion between the margins of the basal 

 and apical parts is as 3 to 2 for the broad, 

 and 2^ to 2 for the narrow triangles. From 

 these several considerations it might certainly 

 have been expected, supposing that worms 

 seized hold of the triangles by chance, that a 

 considerably larger proportion would have 



