PHYSIOLOGY OF THE INVERTEBRATA. 91 



In the words of Dr. MacMunn {loc. cit., p. 189), "the 

 I'adicle indol is furnished by the action of pancreatic ferments 

 upon food proteids ; and as the so-called liver of Invertebrates 

 is really a pancreas in at least some of its functions, possibly 

 some such radicle may be changed by a ferment furnished by 

 the ' liver ' into enterochlorophyll." 



Not only is the digestive fluid of Zumbricus capable of 

 acting upon starch (as already stated), but it readily attacks 

 cellulose ; this fact agrees perfectly with the kind of food- 

 stuffs which the earthworm consumes. 



(c) The Polychceta. — In Nereis, a pair of salivary glands 

 are appended to the base of the proboscis. The secretion 

 obtained from a large number of these glands readily con- 

 verted starch into dextrose. 



Concerning the digestive fluid of Nereis pelagica (a marine 

 species). Dr. L. Fredericq performed the following experi- 

 ments : — Sixty of these worms, which had been preserved in 

 alcohol for six months, were dried and pulverised. From the 

 pulverised mass the various aqueous extracts (neutral, 

 alkaline, and acid) were prepared. Fibrin was dissolved after 

 a few minutes in the alkaline extract ; at the end of a little 

 longer time in the neutral extract ; but remained intact for 

 many days in the acid extract. The liquid resulting from 

 the digestion gave distinctly the reactions of peptones with 

 copper sulphate and potash. 



The same experiments repeated with fresh specimens of 

 Nereis gave the same results. The digestive power of the 

 alkaline extract is considerable ; for it can digest, in less 

 than two hours, a quantity of fibrin equal to the weight of 

 the worms employed in making the extract. 



The Insecta and Akachnida. 



We now proceed to the Insecta and Arachnida, and, as 

 examples of these two classes, we describe in detail the 



