816 PROFESSOR J. STEPHENSON ON 



which supply at most y-oW ^^ their material needs by digestion of solid food {Suherites, 

 Octocoralla, Rhizostomata) ; (5) that animals can live and produce ova altogether with- 

 out solid food, that the progeny grow, undergo ecdysis, and develop at the same rate 

 as animals under the usual natural conditions, all without solid food (Max Wolff on 

 Simocephalus)." 



My observations on the Polychseta and aquatic Oligochseta serve to show that the 

 introduction of water into the alimentary canal by the anus is a much commoner 

 phenomenon than has hitherto been recognised, and hence give some support for 

 the application of Putter's views to these groups. 



In this connection it is interesting to consider the exceptions to the rule of the 

 prevalence of intestinal respiration, both in the lower Oligochseta and the Polychseta. 

 In the lower Oligochseta (not counting the Enchytrseidse, which are not principally 

 aquatic) the most marked exception is that of the genus Chsetogaster. This is, so far 

 as I know, the only carnivorous group of aquatic Oligochsetes ; specimens will ingest 

 auimals or portions of animals of a relatively considerable size ; indeed, they will attempt 

 to swallow animals much larger than themselves. Of the Polychseta, excluding doubt- 

 ful cases and those in which there is no evidence either way, the families in which, so 

 far as my observations go, ascending ciliary action in the intestine does not occur, are 

 the Phyllodocidae, Eunicidse, and Ariciidae (the Aphroditidse are not reckoned, their 

 intestinal respiration being of another type). These are all placed in the group 

 Nereidiformia ( = Rapacia) by Benham, a group composed for the most part of active 

 carnivorous forms with armed proboscis (Fuchs places the Ariciidse with the 

 Spioniformia). 



It is precisely these carnivorous forms which, since they ingest comparatively large 

 masses of solid food, approach nearest in their manner of feeding to such higher animals 

 as birds and mammals. It is possible to suppose, therefore, that these forms are 

 capable of supplying themselves in this way, and do supply themselves, with the 

 required amount of nutriment. The absorption of dissolved matters is no longer 

 necessary ; a continual circulation of water through the alimentary tract would even be 

 harmful, as diluting to too great a degree the digestive juices poured out for the 

 purpose of acting on the solid masses. It is comprehensible, therefore, that it should 

 be among these forms that the exceptions to the rule of intestinal "respiration" are 

 found to occur. 



III. GENERAL CONSIDERATIONS. 



The posterior part of the alimentary canal, with the anus, is in most of the higher 

 animals the channel by which the food-remains are got rid of, and in them it subserves the 

 function of expulsion practically exclusively. But widely distributed, as we have seen, 

 among the aquatic Oligochgeta and the Polychseta there is an inhalant function as well ; 

 and it is perhaps worth while inquiring whether the expulsive or the receptive function 

 is likely to be the more primitive. In other words, is it probable that such a funda- 



