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THE AMERICAN NATURALIST [Vol. XLVIII 



It is evident that these bristles form a group of twelve 

 in four rows of three each. 



This arrangement is recorded as 3, 3, 3, 3, the separation into rows 

 being denoted by commas. 



When one or two of the anterior bristles of a row are omitted, the row 



In order to denote tl/omission of the second or third bristle when 

 those anterior to it are not omitted, the normal positions of the bristles 



the second bristle would be called ac. 



Addition of a supernumerary bristle into a row is denoted by ! in- 

 serted in the proper position between or in front of the letters denoting 

 the normal bristles. Thus addition of a bristle in front of a row would 

 be expressed by calling the row !abc. 



Insertion of a supernumerary brist 

 denoted by parentheses enclosing a. b. or acordnig to tne powiiu- 

 of the bristle from anterior to posterior. Thus a definition as 3, (a), 

 3, 3, 3, would denote the addition of a bristle between the first left post- 

 dorso-central and the first left post-acrostichal. 



Additional bristles are usually smaller than the normal, but range all 

 the way from microchaeta? to the size of the normal macrochaets. A 

 small bristle is denoted by italics. 



The progeny of a few wild females have been bred and 

 counted since my previous paper. 3 These have been 



the normal 



