EXPERIMENTS ON DIGESTION. 215 



slice of tlie same fish was folded longitudinally over a 

 similar bit of litmus-paper, and given to a Crassicornis. 

 If any acid secretion were present, the paper would redden ; 

 if not, the blue colour would remain. On the following 

 morning the ejected morsels were examined, Init not a trace 

 of acid reaction was visible. Eepeating the experiment 

 several times under varying conditions, I came to the con- 

 clusion that no acid fluid was present in the digestive 

 process of the Actiniae. There still remained a doubt. 

 Solvent secretions are either acid or alkaline. It was neces- 

 sary to make similar experiments with an alkaline re-agent. 

 This was done, and with similar results. It is worth noting 

 that M. Hollard equally failed in detecting an acid or alka- 

 line reaction,* which is a confirmation of my experiments. 



The Actiniae do not effect their preparation of nutriment 

 by chemical means ; and in our strict sense of the term, 

 they cannot be said to digest. I was anxious to see how 

 far mechanical means were employed, a^nd for this, Reau- 

 mur's admirable experiment was a guide. In his day it was 

 supposed that digestion was a purely mechanical operation, 

 the food being ground into a pulp in the stomach. He took 

 hollow silver balls, perforated with holes, and filling them 

 with meat, caused them to be swallowed by a dog. When 

 they had remained a suitable period in the animal's stomach, 

 they were withdrawn by the thread attached to them. If 



* " II est remarquablo, et je m'on suis souvent assur^, que les papiers 

 reactifs plonges dans cet organe, et dans la cavite infiSrieure, soit au moment 

 de la digestion, soit chez 1' animal h, jedn, no donnent aucun indice d' acidity, 

 ni d'alcalinitd." — "Etudes Zoologiques sur lo genre Actinia. " — Revue et 

 Magaziii de Zoolojie, No. 4. ISoi, 



