the Geometrina of the European fauna. 125 



kindly accumulated from correspondents, and sub- 

 sequently examined the neuration of, a considerable 

 number of specimens of the commoner British species, 

 and thus enabled these observations to be established 

 on a wider basis than could otherwise have been the 

 case. 



In the following results the species are arranged in 

 the order of the preceding classification. All the species 

 of the family are given, except where no variation was 

 found within the limits of the genus ; in such cases tlie 

 generic diagnosis sufficiently expresses the result. The 

 number enclosed in brackets following the name of tbe 

 species gives the total number of specimens examined ; 

 that which follows each statement of neural characters 

 gives the number of specimens found to display characters 

 in accordance with such statement. As a rule, more 

 pains have been taken to examine a number of specimens 

 in those species where the examination of a few indicated 

 liability to variation. In interpreting the statement of 

 characters, it must of course be remembered that, as 

 usual, veins 10 and 11 are understood to be free and 

 separate so far as they are not expressly stated to be 

 otherwise, I would mention also that the accurate 

 ascertainment of the neuration in an individual of this 

 family is commonly much more difficult than might be 

 supposed ; the veins in question are nearly always very 

 close together throughout their course, and a tendency 

 to connection is often shown where no actual connection 

 exists ; on the other hand, the connecting bar is fre- 

 quently hard to observe, and really doubtful cases some- 

 times occur. Allowance must be made for these diffi- 

 culties ; but I think the results are not without value as 

 a numerical record of structural variability. I might 

 also point out to those who advocate the naming of mere 

 varieties that these examples of structural variation are 

 at least as worthy of the dignity of a name as any 

 examples of colour variation ; so that in the case of a 

 species with perhaps six colour varieties and as many 

 structural, the various combinations would require no 

 less than 36 names. 



