27 



The same result was invariably obtained for a period of 

 about two months; in the protein-free filtrates I never got 

 positive results with ninhydrin tests. 



The digests had a slightly acid reaction which is optimal 

 for autolysis. Yet autolysis seemed to proceed exceedingly 

 slowly. This may of course have different reasons : it is possible 

 that the proteins of these tissues have a great resistance 

 against proteolytic enzymes. We saw in the chapter on the 

 enzymes that other proteins are digested much more rapidly, 

 this might be an indication in this direction. It is also possible 

 that the conditions of reaction were very unfavorable; from 

 what we know about autolysis in other forms, ■ this does not 

 seem very probable however. In the third place it is very 

 well possible that the quantity of enzyme at hand is very 

 small. 



Autolysis occurs however, and this was more evident yet 

 when I dialysed a small quantity of thr digest through a thin 

 collodion sac. A strongly positive ninhydrin test in the outside 

 liquid showed that amino-acids though they did not show up 

 in the protein-free filtrate are surely present. 



The same thing proved to be the case in autodigests of 

 Thyone guts. No trace whatsoever of autolysis could be 

 obtained in the protein-free filtrates. The guts remained in 

 unliquified condition for a long time and nothing indicated 

 that autolysis were it even very slight, was going on. Yet 

 when I dialysed part of the liquid, I obtained a positive 

 ninhydrin reaction in the outside Hquid. 



From this evidence I have concluded that autolysis goes on 

 very slowly in the guts of Asterias as well in those of Thyone. 

 There is no doubt however as to whether it actually takes place. 

 And there can in that way be no doubt that a proteolytic 

 enzyme must be present in their guts. 



But one thing is very evident on the other hand, i. e. that 

 in these form this process does not take place with the same 

 intensity and rapidity as in the higher forms on which bioche- 

 mists have been working up to the present day. The solution 

 of the problem why this is the case, must be left open for a 

 more detailed investigation. 



9. CONTENTS OF THE GUT OF THYONE. 



In studying the contents of the gut of a particular species, 

 we can on one hand get some information about the natural 

 food of the species, on the other hand we may get an idea 

 about the enzyme activity in their gut. 



For the present study I used animals which had been brought 

 into the laboratory on the same day on which the observation 

 was made. Their gut-contents were put on a slide and examined 

 through the microscope. 



