48 INHERITANCE IN SILKWORMS, I 



wings which were perfect and available for study. R 3 is present and 

 normal in 27 of the 46 left wings and in 22 of the 43 right wings. R 3 

 is entirely absent as a separate branch in 29 of the 46 left wings and in 

 21 of the 43 right wings; R 3 is present in part of its length in three 

 wings as follows: (a) as a very short branch originating typically 

 but ending freely in cell R 2 % of its length from the costal margin, in 

 I left wing (specimen Sub. 4, I) ; (b) as in above under (a) but 

 twice as long in i left wing (specimen Sub. i, B) ; (c) in three sections, 

 a basal, a terminal, and a middle section lying freely in cell R 2 in i right 

 wing (specimen Sub. i, R). 



The variations in the anal series of the fore wings affect the first 

 and third anal veins. In the case of the first anal vein, the variations 

 in 95 wings may be summarized under the following four classes: (a) 

 4 right and 5 left wings in which there is not a trace of the vein; not 

 even a fold, furrow or surviving trachea; (b) 39 right and 33 left 

 wings in which there are faint traces of a thickening or a faintly defined 

 vein distally and not extending for as much as ^2 the total length of 

 the vein; (c) 5 right and 2 left wings in which as much as the distal 

 half of the vein is present as a vein, fold, furrow, thickening or trachea 

 or any combination of these; (d) I right and 3 left wings in which the 

 distal ^, ^3 or 24 of the vein is present as a vein. In no case is the 

 vein found present in its entire length. 



The third anal vein is also represented by all stages between and 

 including total absence on the one hand and presence entirely on the 

 other: (a) in 4 right and 2 left wings the vein is absent; (b) in 32 

 right and 35 left wings the vein is represented in part of its length by 

 a fold, furrow, thickening or surviving trachea or combinations of 

 these; (c) in 4 right and 3 left wings the vein is almost complete; (d) 

 in 7 right and 5 left wings the vein is present in its entirety. 



The other variation by loss in the fore wing consists of the absence 

 of the cephalic, caudal, or middle third of the medial cross vein. 



In the hind wing the variation by loss of parts concerns the medial, 

 cubital and anal series of veins. 



The variation by loss in the medial series of the hind wing consists 

 of an incomplete condition of M 2 : (a) in i left wing M 2 is only ^ 

 its normal length, stopping short of the outer margin (specimen, Sub. 

 i, N); (b) in i left wing the chitinization of the base of M 2 is 

 incomplete (specimen Sub. 3, B). 



The variation by loss in the cubital series of the hind wing consists 



