SECT, in THE A!' PI'; NO AGES 27 



into the other arc due to adaptation to the browsing 

 manner of life. 



Our deduction of Apus from an adult carnivorous 

 Annelid, which gradually adopted the habit of bending 

 round its head, and of using its parapodia for capturing 

 its prey and pushing it into its mouth, gives us at once 

 the general direction along which we should expect 

 modification to take place. First of all we should 

 expect the parapodia along the whole length of the 

 body to be bent round towards the ventral middle 

 line. Further, the dorsal and ventral branches of 

 these parapodia would be somewhat differently de- 

 veloped in adaptation to the various needs of the new 

 manner of life. The ventral parapodia on the three 

 posterior head segments would be differentiated into 

 jaws and maxillae, while on the anterior trunk seg- 

 ments they would serve to rake food into the middle 

 line and forward it towards the mouth. The uses to 

 which the dorsal parapodia could be put are not so 

 apparent. Since, however, the habit of browsing 

 necessitates a certain amount of locomotion, we may 

 safely conclude that they would be utilised for this 

 purpose. The original Annelid in its Annelidan 

 days no doubt moved in the typical manner of 

 Annelids by the alternate extension and contraction 

 of the body. As, however, the body of our Crustacean 

 Annelid shortened and began to develop an exo- 

 skeleton, some other method of locomotion would 

 become necessary. The dorsal parapodia would thus 

 naturally be brought into requisition. The same 

 efforts which brought the ventral parapodia round 



