272 THE ZOOLOGIST. 



(4) The sense of touch was developed to an extreme degree, 

 the slightest contact with the glass causing the worm to stop 

 work and contract, a sure sign that it appreciated the proximity 

 of danger. 



(5) However, when the provocation proved of a natural order, 

 such, for instance, as a glass rod inserted into the soil in imita- 

 tion of a burrowing mole, the worm would penetrate the soil 

 quickly, making its way to the surface and not deeper into the 

 soil. This seems to point to the fact that worms can discrimi- 

 nate between disturbances of the soil caused by various means, 

 and also that they instinctively seek the surface, knowing that a 

 mole would avoid the light as much as possible. 



(6) When it was placed on a fairly smooth surface it in- 

 variably moved in a circle, the larger head always being towards 

 the centre of the circle. 



(7) In its progress, the larger head expands and contracts 

 in point of time slightly in advance of the smaller, showing 

 that the greater degree of sensitiveness is placed in the larger 

 head. 



(8) Again, when the progress of the worm was barred by 

 placing a pin vertically at the forking of the heads, it was 

 invariably found that the worm passed the pin by allowing the 

 larger and not the lesser head to slide past the obstruction, 

 which confirms the surmise that greater sensitiveness is possessed 

 by the larger head. 



The above are some of the observations briefly stated. 



Before bringing this paper to a close, it might be stated that 

 concerning the embryological study of Variation we have the 

 results of Roux and others concerning the segmentation of the 

 metazoon ovum, showing that in certain species the first cleavage 

 plane divides the body into the future right and left halves of 

 the adult animal.* 



This suggestion, which is an old one, received support from 

 the fact of Meristematic Variation, especially the formation of 

 homologous twins and double-headed monsters, which are shown 

 to arise from one ovum by division. (Vide Driesch, Zt. f. w. Zool. 

 1891, liii. p. 160.) 



* It is the second cleavage in many cases. (Vide E. B. Wilson, Anat. 

 Anz. vii. 1892, p. 732.) 



