57 



puscles as the chief transporters of food, other authors also 

 attribute considerable importance to their activity in the service 

 of digestion. Among these authors is Chapeaux 15), who 

 considers them as especially important in the digestion of fats. 

 In chapter 16 we saw that in some respects he exagerated their 

 importance and that I have never been able to observe the 

 emulsification of fats by the intestinal juices which he found. 

 He states that the emulsified fat passes through the gut-wall 

 without any chemical change but gives no experimental proof 

 for his contention. 



tt La dissolution s'opere dans la cavite generale" ; hydrolysis 

 takes place here by the corpuscles, as the change in reaction - 

 which I have critisised in chapter 18 indicates. If 



olive oil is injected into the perivisceral fluid, the amibocytes 

 ,,eat" it. That such experiments do not prove much, will be 

 discussed in the chapter on excretion. 



There is one small problem, however, which he does not 

 attack. Is there any increase in fat in the corpuscles after fat- 

 feeding ? in other words, can we actually prove his hypothesis that 

 the fat would not be changed chemically during its passage through 

 the intestinal wall, that it would then enter into the perivisceral 

 fluid and finally be tt eaten up" and hydrolysed by the amibo- 

 cytes? I have made experiments of this kind repeatedly (on 

 Arbacia), but always with negative results. Except in two cases 

 in which the coelomic cavity contained very large drops of oil 

 probably on account of the breaking of the intestinal wall, I ne^er 

 found a trace of free oil Neither could I observe an increase oi 

 fat in the corpuscles. Centrifuged corpuscles of injected animals 

 were put on a slide and treated with Flemming's fluid, as was a 

 control sample. I never could see any difference between two 

 such samples though they were withdrawn at various periods of 

 time after the feeding. For this reason I am rather inclined 

 to believe that Chapeaux is wrong in his hypothesis. 



In the chapter on the perivisceral fluid we saw that this 

 liquid is by no means absolutely stagnant and motionless, 

 makes it possible that such functions as the distribution of food 

 could be taken care of by this medium. 



To study this problem I made some very simple experiment: 

 on Arbacia. Food solutions (e.g. solutions of cane-sugar or 

 casein as the most simple carbohydrate and protein) were in- 

 jected into the digestive tract of the animal. 



Feeding experiments never had any success, 

 animals, urchins, starfishes and cucumbers refused to tak 

 food in captivity, even if their natural food was presented 

 them. Starfishes, put into one basin with either mussel 

 sea snails (e. g. Littorina), never ate any of them. 



In this respect I was very unfortunate. plans 



animals stained with some vital stain to our Echinoderms 



