RESPIRATION OF APHRODITACE.E. 333 



two specimens procured at the same time, one was 

 large and fine, two inches and a half in length, the 

 other not quite half as long, but proportionally 

 broader. After living peaceably together during two 

 or three days, the former was found attempting to 

 devour his companion. One half was already swal- 

 lowed into its strong and capacious proboscis, while 

 the victim struggled desperately to be free. How- 

 ever, the assailant, after retaining the prey for some 

 time, was reluctantly compelled to disgorge it ; but 

 the suffering animal's back was broken, and some of 

 the scales ruffled off by the rude assault. Next 

 morning only half of the poor fellow remained, the 

 other portion having been devoured ; and the victor 

 now darted out its proboscis repeatedly, in order to 

 finish its meal on the rest, as it lay in a corner. 



The AphroditacecB constitute a group of Annelides 

 to which the term " dorsibranchiate" does not strictly 

 apply, seeing that in the majority of the species be- 

 longing to this family no branchial appendages exist 

 either on the back or anywhere else. Respiration is 

 performed on a novel principle, of which no illustration 

 occurs in any other family of worms. The whole 

 back is vaulted over with a series of broad scales, or 

 membranous plates, which exhibit periodical move- 

 ments of elevation and depression. Overspread by a 

 coating of felt, readily permeable to water, the space 

 beneath these scales during their elevation becomes 

 filled with a large volume of filtered water, which 

 during the descent of the scales is forcibly ejected 

 at the posterior end of the body ; thus, like a pair 

 of water-bellows, supplying a constant flow of the 



