22 



free filtrates of any of the digests. In many cases I could convince 

 myself, that starch which was added as such or after it "^d 

 been boiled for a few minutes, was still present. The blue 

 coloration which the digest assumed with J in KJ proved this 

 clearly. 



Though Feh ling's test was entirely negative in all cases, 

 Benedict's reagent gave results which were neither positive 

 nor negative. In some of the digests I found that the blue 

 coloration had disappeared and in its stead a red color was 

 seen. Maybe this is to be explained in the following way : 

 Biedermann 8) found that ,.durch das Mitteldarmsecret einer 

 Raupe aus Starke fast nur Erythrodextrin und nur sehr wenig 

 Zucker gebildet wird." He concludes that we have to do here 

 with an amylolytic enzyme entirely different from that in snails 

 and other animals. This might account for my observations 

 which greatly puzzled me during my stay in W oodsHole. Since 

 however Biedermann's paper came too late to my attention, 

 unfortunately I could not study this problem more in detail. 



c. Lipolytic enzymes. 

 For these I refer to chapter 16. 



7. ARE THE ENZYMES PRESENT IN THE FREE FORM ? 

 PHAGOCYTOSIS IN ECHINODERMS. 



A question of great importance is whether the enzymes on 

 which we have reported in the preceding chapter, are present 

 in the free form. 



We know that in unicellular organisms the whole process 

 of digestion is an intracellular one. In a single food-vacuole 

 everything is digested, all enzymes are secreted and even diffe- 

 rent degrees of acidity are realised here successively. 



In pluricellular organisms, in their most primitive forms, the 

 same state of affairs persists. This is especially true of the 

 lower worms, the coelenterates and the sponges. The entoderm- 

 cells of these animals can easily be compared with protozoa 

 of different groups, which take care of one of the functions in 

 the service of the organism as a whole. The chemical destruction 

 of the food which prepares the same for the assimilation by 

 the living substance, is in that way originally a purely cellular one. 



The excellent study of Jordan 66) on digestion in Actinians, 

 gives a clear idea of phagocytical processes of this kind. And 

 yet the process is in some way complicated here; the large 

 prey of these animals necessitates a device of some kind for 

 breaking them down. M e s n i 1' s hypothesis (Ann. Inst. Pasteur. 

 T. 15. 1901 p. 352—397), that a kind of dissection and frag- 

 mentation by the rims of the saepta would take place, aided 

 by a small quantity of proteolytic enzyme, secreted on contact. 



