160 



Inez Whipple Wilder. 



From these statistics we see that the iiiiniber of tubules upon one 

 side varies from one to six, the number upon the two sides of one 

 individual being, however, approximately equal. Moreover, the 

 tubules, where more than one are present, vary much in length, as do 

 also the longest and the shortest tubules of different individuals. Thus 

 the range of length in three individuals of approximately the same 

 size (Nos. 1, 2 and 4) is from 0.21 mm. to 3.09 mm. and the 

 extremes are found in the same individual. The longest tubules in 

 these three individuals vary from 0.83 mm. to 3.09 mm. It is notice- 

 able, moreover, that when there are only two tubules the more lateral 

 is the longer ; while in a set of three or more the longest one is the 

 middle one (or one of the middle ones) of the group. For example, 

 the set of six on the right side of specimen No. 3 is disposed in three 

 groups, the medial group consisting of two short ones, the lateral 

 group of three, two short and one much longer, while between these 

 two groups lies the middle tubule which is the longest of the six. 

 There is a noticeable symmetry in the approximate length of the 

 tubules on the two sides of an individual. Although the shortest 

 specimen (No. 1) has the smallest number of tubules, and also 



