488 W. WILLIAMSON AND C. D. SOAR ON BRITISH HYDRACARINA : 



of the body. On the dorsum is the yellow fam-shaped (r) figure 

 indicating the organ variously designated as the excretory organ 

 and as the Malpighian vessel. The dark colour of the venter is 

 relieved by white and yellow specks. The legs are transparent 

 and tinged with green. Thor points out to what extent the colour 

 of the body responds to various preservative solutions, and the 

 necessity for caution in identification of preserved material in 

 those cases where colour may be of some value in assisting 

 identification. The palpi range from 0*40 mm. to 0*55 mm. in 

 length, and are more slender than the first pair of legs. The 

 second, third and fourth segments are covered with fine pores 

 clustered together in groups, which are distributed fairly evenly 

 over the segments. The bristles and hairs found distributed 

 over the segments appear to be fairly constant in the sub-genus 

 to which our species belongs. The first segment has only one 

 slightly curved bristle at the distal extremity of the extensor 

 surface. The second segment has three similar ones about 

 the middle of the extensor surface, and at the distal extremity, 

 but just towards the inner side, two long hairs about as 

 long as the third segment. The long bristle at the distal end 

 of the ventral or flexor surface is about as long as the segment 

 itself, and is minutely pectinate. The third segment has five 

 bristles, two about the middle, close to the extensor surface, and 

 three extremely finely pectinate ones at the distal inner sur- 

 face, one at the flexor edge and two at the extensor edge. The 

 fourth segment has five fine hairs on its extensor surface, one 

 in the posterior one-third, one about the middle, and the other 

 three scattered about the distal extremity. The flexor surface 

 has only one pore and rudimentary hair in its distal third. 

 Concerning the function of the long flexor bristle of the second 

 segment, Thor points out that when the palp is flexed, the 

 bristle can enter the mouth and by a slight lateral movement 

 can also enter the glandula globulosa. Thor's conjecture of the 

 function may be expressed thus the bristle enters the pore of 

 the glandula globulosa, and by means of the pectination some 

 of the secretion adheres to it. The secretion may then be 

 conveyed to the claw of the mandible, and thus be used to 

 paralyse the victim whose juices are to be extracted, or it may 

 be conveyed by the bristle direct to the wound which the claw 

 has made. 



