XX ON THE TERMINOLOGY OF DIPTERA. 



vein ; the second belongs to the first section of the posterior part 

 of the wins;, and extends as far as the anterior basal transverse 

 vein ; the third belongs to the second section of the same part of 

 the wing, and joins the posterior basal transverse vein. These 

 three cells may, in general, be called the three basal cells (cellulse 

 basales). The foremost of them is generally much longer than the 

 two others, a proportion which is usually indicated by the expression 

 of "one large and two small basal cells ;" against this mode of ex- 

 pression nothing can be objected, since it implies no uncertainty. 

 It is, however, a little puzzling to invent a convenient term, when 

 the posterior basal transverse vein, instead of running to the sixth 

 longitudinal vein, assumes the character of a longitudinal vein, 

 and runs to the border of the wing, so that the hindmost basal cell 

 joins the border of the wing. Not only in this case, but also when 

 the hindmost basal cell, though closed, is distinguished from the 

 second basal cell by a much more considerable length, it is usually 

 named the anal cell (cellula analis), and then, consequently, two 

 basal cells are considered to be present. Badly chosen as the term 

 "anal cell" may be, it is, nevertheless, so settled that it will be 

 difficult to remove it by the introduction of a more convenient one. 

 In certain families the great and very symmetrical development of 

 the three basal cells is characteristic; they are then called the 

 ternated cells (cellulse tematse), which term, though expressive 

 of the thing, seems to be superfluous. One of the most important 

 cells is that belonging to the first section of the posterior part of 

 the wing, and extending from the anterior basal transverse vein to 

 the posterior transverse vein, and bearing the little transverse vein 

 on its anterior margin ; it is generally called the discoidal or discal 

 cell (cellula discoidalis). When the anterior basal transverse vein 

 is wanting, which is characteristic in many families and genera, 

 this cell coalesces with the second basal cell, which then must be 

 considered as a part of the discoidal cell ; if the posterior trans- 

 verse vein has disappeared, there is no discoidal cell at all. In 

 those Diptera which possess the anterior intercalary vein, sometimes 

 the part of the posterior transverse vein situated before or behind 

 this intercalary vein is wanting, and in that case the existence of a 

 discal cell is granted, which, in the former instance, is considered 

 as anteriorly opened, in the latter, as posteriorly opened. 



The second cell of the middle of the wing opening in its border, 

 and those of the two first sections of the posterior part of the 



