4 8 



THE 



PART I 



their muscles (see Fig. 12, p. 55) that what the 

 gnathobases held between them would be rapidly 

 forwarded towards the mouth. The disappearance of 

 the gnathobases, excepting on the most anterior 

 trunk limbs the maxillipedes in the majority of 

 modern Crustacea, is explained by a change in the 

 manner of life. As the trunk limbs became more and 



FIG. 10. The last rudimentary trunk limb (L. prodnctns), \ mm. in length. Lettering 

 as before. It is seen to be a typical Phyllopodan limb. 



more purely locomotory organs, such as ambulatory 

 legs, and as other methods of capturing prey were 

 acquired, the ventral parapodia would degenerate, not 

 only from having lost their function, but as positive 

 hindrances to the free movement of the limbs. 



The most distal appendage, on the first limb of 

 Apus, is a probably functionless scale (Fig. 9), and in 

 the following limbs it is a toothed claw (Fig. 4), while 



