1889.] NEW-YORK MICROSCOPICAL SOCIETY. 35 



The hairs of the second order are short, somewhat club-shaped, 

 and occur in rows of single file, one row on either extremity of 

 each segment. Their structure is almost identical with that of 

 the hairs of the first order, only their spines seem to stand out a 

 little more laterally. The hairs of the third order I have called 

 " arrow-hairs," because they resemble nothing so much as 

 miniature arrows. This name however can only convey a gene- 

 ral idea of their outward appearance. In the wonderful elabo- 

 rateness of their design and the details of their structure they 

 are very different from any arrow ever made. 



The " arrow-hairs " are usually situated in single rows between 

 the pairs of rows of club-shaped hairs. But each of the last 

 three segments, instead of a single row, carries a dense tuft of 

 '* arrow-hairs," closely packed with their points standing out like 

 a forest of spears. Their shaft is cylindrical, and carries from 

 twenty to forty spiny whorls, resembling little funnels placed 

 one inside of and slightly above the other, or more, perhaps, a 

 child's necklace of lilac blossoms. These whorls are angular, 

 with four spiny processes hollowed out like a cup. They are 

 succeeded by a sort of shield, a structure agreeing in general 

 outline with the spiny whorls, but of at least double the dimen- 

 sions of the latter. Above this shield, and connected with it by 

 a sort of neck, arises the arrow-head. This is conical in shape, 

 and is about five times as long and two or three times as broad 

 as one of the spiny divisions. The "system of four," notice- 

 able in the whorls and shield, is here also maintained, but 

 instead of bristling spines we have here long ribs, which form 

 an elaborate system of barbs at the base rising to a point at the 

 apex. 



Under a " quarter-inch " objective the extremity of the arrow 

 does not appear very sharp, indeed it is almost a little rounded, 

 But in reality it is wonderfully fine and many times sharper than 

 the sharpest needle. Fifty of these hair-extremities could be 

 crowded into the space occupied by the point of a fine needle. 



I draw attention to this because it has a bearing on the theory 

 which I have formed respecting the function of these hairs. In 

 my opinion these hairs, pretty and graceful though they appear, 

 are not intended for ornamentation, nor are they the remnants 

 or rudiments of appendages whose usefulness lies buried in the 

 past. There can be little room for doubt that they are of great 



