H 



there appeared to be a peculiar synchronism in the feeding 

 habits of different specimens. On certain moments of the day 

 almost all the animals had their gut either completely full or 

 halfway full or empty. In this way he could observe that as 

 a rule the contents of the gut are changed about three times 

 a day. By determining the number of animals present in dif- 

 ferent localities around the Bermuda's this is very easy 

 since the big animals are clearly visible through the transparent 

 water of the tropical sea , he could figure out the amount 

 of sand displaced in a certain amount of time. Restricting him- 

 self as far as necessary in his assumptions, he came to the 

 conclusion, that in areas frequented by this species, roughly 6 

 to 7 kilo's (dry weight) of sand passes through Holothurian 

 guts per year and per square meter. In the enclosed sink, 

 Harrington Sound, he finds that the quantity eaten annually, 

 is something like 500 to 1000 tons. 



These figures illustrate more clearly than speculation could 

 the tremendous importance of these animals and show ,,that 

 the feeding activities of these animals may have an effect on 

 the sea-bottom not unlike that, so carefully described by 

 Darwin, which earthworms produce in the soil." This is the 

 more probable, because as we will see later on, the gut con- 

 tents of this species are fairly acid, so that calcium carbonate 

 is brought into solution. 



5. TOXICITY OF THE STARFISH STOMACH. 



In almost every popular description of the attack of a starfish 

 on bivalve molluscs, we are told that the starfish after having 

 opened the shell, drops a few drops of ,,poison" on the prey 

 and facilitates his work in that way. It seemed to me to be 

 worthwhile to investigate this question a little more closely 

 from the experimental side. The question, formulated more strictly, 

 is : Does the stomach of the starfish secrete a substance which 

 is poisonous to the muscles or in general, to the contractile 

 tissues of the prey? In that way the secretion of the stomach 

 would have a double function : 1 . to kill the prey or at least 

 to abolish the tonus of the adductor muscle, 2. to dissolve the 

 tissues more or less completely in order to make them fit to 

 enter into the stomach or the radial sacs. 



The fact that as E ud es-D e si on g champs reports if an 

 oyster is taken away soon enough, it is dead even if it has not been 

 dissolved, pleads in favor of this hypothesis. If it had been 

 dead previously, it would smell as strongly as all decaying sea 

 material does ; this is not the case. W. H e s z 59) also believes 

 in the presence of a toxic substance. Cuenot 22) speaks of a 

 toxic mucus (,,glaire"). The same mucus is according to him 



