21 



autolysis and that on the nitrogen metabolism of Holothurians 

 we will discuss his arguments more in detail ; here I only 

 mention my own experiments. 



Several digests were made in which either egg-white or 

 gelatin, Na c CO 3 or HC1 were used as described before. 



After one week and a half the following tests were made : 



Table 2. 



The amino-acids which could not be demonstrated in the 

 protein-free filtrates soon appeared to be present in dialysates. 



Summarising our results on the proteolytic enzymes, we may 

 say, that only one enzyme is present, i. e. trypsin, which possibly 

 works over a wider range of PH than the same enzyme in 

 mammals, but that no pepsin is found. The enzyme is present 

 in all groups studied. 



b. Sucrolytic enzymes. 



Invertases are also present in the three groups. Experiments 

 of exactly the same nature as those described above, were 

 made, in which cane-sugar (glucose free, the so-called rock-candy) 

 was used as a substrate. The enzyme is much stronger in the 

 starfish and Thyone, than in Arbacia in which form it is 

 very weak. The same observation was made byCohnheimin 

 Sphaerechinus granularis. This author considers the mvertase 

 in the starfishes as an adaptation to a sweet, but not reducing 

 sugar of unknown nature present in bivalves around Naples. 



As far as the amylolytic enzymes are concerned our experi- 

 ments were complete failures. I do not know whether I must 

 blame this on my method, because I used the organs themselves, 

 be it after having crushed them with sand, instead of extracts, 

 as they have mostly been used by previous authors 1 ). At any 

 rate, I did not get any positive Fehling's tests in the protein- 



*) Fredericq 40), Griffiths 48), Chapeaux 15) and Clerc 16*) 

 found an amylase present in starfishes; Krukenberg, Cohnheim 17) and 

 Henry 53) in sea-urchins; Clerc 16 a ) and Cohnheim 17) in cucumbers. 



