272 THE APODID^: PART n 



being chiefly due to the bending down of the head in 

 order to bring it within the shells (Fig. 61). 



Limnadia and Estheria show the process com- 

 pleted, i.e. the head bent down to such an extent as 

 to be entirely enclosed between the bivalve shells 

 (Fig. 62). The position of the head in these animals, 

 bent ventrally downwards, is in striking contrast to 

 that of the Ostracoda, which is situated far back 

 in the shell and looks forwards. 



We must here leave this interesting subject in the 



FIG. 62. Estheria Donaciiormis Baird 9 > to shovy the completion of the process of 

 bending the head into the bivalve shell. 



hope that some one may be induced to attempt to 

 build up a natural order of the Phyllopoda, and 

 endeavour when possible to show how, and under 

 what biological laws, the different forms have arisen 

 from Apus. 



THE MALACOSTRACA. 



We come lastly to the most highly developed 

 group of the modern Crustacea the Malacostraca. 

 We need not say much about these. By deducing 



