TWO NEW LICE. 



259 



sac ; it then presented the appearance of a dice-box in a glass 

 bowl. The specimens were in too poor a state of preservation 

 for histological examination, but both the sac and the upper 

 part of the duct appear to be chitinised, while the lower part, 

 which could not be traced, is of peculiarly elastic nature and 

 capable of being pulled out a long distance. 



Text-figure 9. 



Polj/phtx oxyrrhynchus. Spermatheca. 

 A. Sac. B. "Funnel." C. Duct. 



In the Siphonaptera the shape and size of the chitinous parts 

 of the spermatheca vary a good deal, and are sometimes used for 

 taxonomic purposes. It is improbable that they will serve this 

 end in Anoplura and Mallophaga. 



Notes on the Tracheal System. — The following description is 

 taken from a preparation of an immature form in Stage III. : — 



There is a pair of abdominal spiracles on each of segments 3 

 to 8 of the abdomen and a pair larger in size on the mesothorax. 

 Text-fig. 5 (p. 253) shows the arrangement of the main branches 

 in the abdomen. There is a posterior commissure in the abdomen 

 and on each lateral diverticulum a posterior root. Anterior roots 

 are absent except in segment 4, where one runs forwards and in- 

 wards as far as the first diverticulum. It will be remembered that 

 a commissure is present in this segment in P. brachyrrhynchus. 



There is, I believe, no longitudinal commissure in the thorax 

 as in Phthirus inguinal/is (6) and JPa>matopi?ms taurotragi (9). 

 The two lateral trunks are continued, one on either side, through 

 the head as far as the antennas, where each splits into smaller 

 branches. Small twigs are given off to the mouth-parts and 



