304 ON THE SCALES ON THE WINGS 



wings, and like them, in every instance that I have seen, the 

 longitudinal striae terminate in marginal striae or canals. 

 These marginal canals may be distinctly traced to pass from 

 the base of the scale down each side of the quill, until they are 

 lost sight of near its point. In one instance, I observed two 

 of these fine filaments or canals projecting from one side of 

 the quill at a short distance from its point, and appearing as if 

 they had been drawn from the wing in the act of separating 

 the scale from it. At the first glance, these striae or canals, 

 passing down the sides of the quill, might be supposed to 

 indicate the thickness of the sides of that organ, and this mis- 

 conception is especially favoured by the quill being really 

 hollow for a part of its length, while near the point it is solid ; 

 but the striae or canals being continued into the solid part, as 

 well as down its sides, the error into which we are liable to 

 fall is quickly detected, and the fact of their being truly a con- 

 tinuation of the marginal striae or canals, may not only be 

 proved by their continuation into the solid part of the termi- 

 nation of the quill, but they may likewise be readily and dis- 

 tinctly traced out of the quill round the base of the scale, and 

 throughout the whole length of its sides to its apex. 



The violence to which the scales were subjected had in 

 many instances broken the quills into short lengths, which, 

 under favourable circumstances, assumed the appearance of 

 so many rings, the central orifice occupying about one-third of 

 its diameter, and as the diameter of the quill has before been 

 stated to be ^ of an inch, we may therefore estimate the thick- 

 ness of its sides to be about ~ of an inch. 



The detached striae were likewise frequently broken up into 

 short lengths, but I could not find any of them either sufii- 

 ciently short or in such a position as to enable me, by the like 

 means, to determine whether they possessed an orifice of 

 similar comparative dimensions to that in the quill ; but sup- 

 posing that to be the case, the diameter of the longitudinal 

 striee being ^.. of an inch, the internal diameter of these minute 

 tubes, supposing them to be such, may then be estimated at 

 about 55^3, of an inch. 



