220 CALIFORNIA ACADEMY OF SCIENCES. 



The above table shows that in nearly every character 

 in which the two suborders differ the Ischnocera have a 

 more specialized organization. That the separation of 

 the two groups is very great is shown by the fact that 

 nearly all the important organs are affected, the heart, 

 tracheal system, and nervous system being the only 

 ones alike in both. The exact systematic position of 

 the Mallophaga cannot at present be determined, since 

 enough of the anatomy of nearly related forms is not 

 known. Packard (1887), however, has shown that 

 they may be closely related to the Psocidee, and 

 Kellogg (1896) has given further evidence of this. 

 But if the Psocidse are the most closely associated with 

 the Mallophaga, in what manner the two groups are 

 related is impossible to say. Until this is known the 

 relationship of the two suborders of the Mallophaga to 

 each other cannot be determined nor that of the fami- 

 lies composing these suborders. 



