WHAT IS DIGESTION? 219 



In former chapters I have illustrated this point, and 

 have again to do so respecting the digestive power of 

 the Sea- Anemones. 



In my note-book is pencilled this brief query, " Do 

 the Actiniae digest at all?" a doubt which, in its naked 

 simplicity, might rouse contempt in the mind of any 

 zoologist accidentally reading it. What 1 here is an 

 animal notoriously carnivorous, and you ask whether 

 it can digest ? Have not you yourself repeatedly fed 

 these animals with limpets and cooked beef? are they 

 not greedy of such food ? It is perfectly true. Never- 

 theless a doubt occurred to me whether they did reaUy 

 digest, in any proper sense of the term ; and I made a 

 note of the doubt, as of a point to be investigated 

 immediately on my arrival at the coast. Experiment 

 should settle the doubt. Before narrating the experi- 

 ments, it will be needful to settle with the reader a few 

 generalities on the subject of Digestion ; since, in point 

 of fact, the interest of the question falls mainly on the 

 general subject, and only wdth a secondary importance 

 on the digestive powers of the Anemones. 



What are we to understand by Digestion ? At first 

 the question seems so easy ; yet the closer it is investi- 

 gated, the remoter seems the possibility of answering 

 it. Let us make a clearance by first discriminating 

 Digestion — as a special function of the intestinal canal 

 — from Assimilation, which is the general property 

 possessed by all living tissues. For an animal to grow, 

 and to repair the waste which the action of life inces- 

 santly produces, it must assimilate, which, as the word 



