THE TERRESTRIAL ISOFODA OF NATAL. 577 



genera, founded on sound structui'al characters. Racovitza 

 (16) has erected the genus Anaphiloscia, Stebbing (17) 

 that of Anchiphiloscia, and Budde-Lund (10) the genera 

 Aphiloscia and Nahia. All of these, however, seem to 

 me to differ from Philoscia in some quite minor feature, and 

 do not help at all. I shall, therefore, for the present place 

 the South African forms in the genus Philoscia; no doubt 

 as more matei'ial is examined it will be possible to separate 

 them into two or three distinct genera, each possessing well- 

 marked characters. 



Writing of this genus in 1908 Stebbing (17) stated: "At 

 present there are a bewildering number of species in the 

 genus Philoscia, many of them very incompletely described, 

 and few, if any of them, completely illustrated. A remedy 

 for this state of affairs will not be easily found. The creatures 

 themselves put difficulties in the way of the student. Their 

 readiness to wander about the world undermines any sys- 

 tematic structure built on geographical distribution. Their 

 variability seems to separate forms which are specifically 

 identical. On the other hand, general resemblance seems to 

 unite forms which, on closer examination, are found to be 

 distinct. Among the appendages the antennas and uropods 

 afford especially useful characters, and these appendages are 

 particularly liable to be detached or broken. The structure 

 of the pleopods, especially those of the male, is more and 

 more acquiring systematic importance." 



An examination of a large quantity of material from 

 different parts of the world has convinced me that the mouth 

 parts, by themselves, are certainly very unsatisfactory for 

 purposes of either generic or specific distinction (1), and this 

 is particularly so in the present genus. Apart from the 

 question of variation, the abdominal appendages (pleopods) 

 are scarcely less so, whilst any classification of the Terrestrial 

 Isopoda founded upon sexual characters always leaves it open 

 for the opposite sex to be described as a distinct species. 



fully agree as to the great value of the antennae and 

 uropoda, and to these I would add the shape of the 



