82 PHYSIOLOGY OF THE INVERTEBRATA. 



mimicry, or act as "screens" for the protection of undep-y 

 lying cells, for protective purposes; and possibly, thougli 

 not probably, they may have a nutritional function, as sug- 

 gested by Haeckel. Whatever may be the true function or 

 functions of animal chlorophyll, one thing is certain — that 

 the pigment is manufactured in the body of the animal con- 

 taining it. In the words of Dr. MacMunn : "I would ask 

 investigators to pause before they decide that when an animal 

 chlorophyll is met with, it has been simply eaten by the 

 animal, and deposited unchanged in its tissues ; they mast' 

 remember that the radicle of chlorophyll, like the radicles of 

 other pigments, may be furnished by the action of the diges-- 

 tive juices of the animal on some substance furnished by the 

 plant, and that the animal laboratory is capable of building 

 up molecules quite as lai;ge as that of chlorophyll. Our own 

 haemoglobin is not the unchanged haemoglobin of our food ;; 

 what is derived from it is broken up and then regenerated ;. 

 and it shows an ignorance of physiology to suppose that 

 chlorophyll should be an exception to a general rule." 



Eeverting once more to the Porifera, Dr. Leon Predericq* 

 has extracted from a large number of sponges a ferment' 

 analogous to trypsin or pancreatin. This ferment acts upon 

 starch, fats, and albuminoids. The author of the present 

 work fully confirms Predericq's researches. The ferment 

 contained in and manufactured by the cells of the Forifem'- 

 converts starch into glucose. It form,s an emulsion with 

 neutral fats, and finally decomposes them into fatty acids- 

 and glycerol (glycerine). The ferment also converts albumi- 

 noids into peptones, which become partially converted into 

 leucin and tyrosin. There is no doubt that the cells of 

 the Porifera secrete a ferment in every way analogous to the 

 pancreatic ferment of higher forms. 



The Echinodeemata. 

 Fredericq has also obtained similar results with maB/ 

 * Archives de 2oologie Ea^irimentale, tome 7, p. 400. 



