Explanation of Plate XXII. 
Portion of eighth abdominal segment 9 of 
(1) G. avis X 30, 
(2) G. rnbi x 30, 
showing chitinous tube and spines in the wall of Bursa. The two 
spines in the specimen of G. avis are so nearly .superposed that 
tiiey will probably appear as one in the reproduced photograph. 
These spines are so variable in G. rn&f, that probably no specific 
differences in them can be relied on. 
