95 



puscles occur however not only in the water vascular system, 

 but also in the wall of the water-lungs e. g. In a preparation 

 of the tip of one of these organs between cover-glass and slide, 

 cells were seen which seemed to be identical with the cells 

 in the Polian vesicles. 



Thus they might also occur in the M blood-system" ; and 

 so in all the three fluid systems, viz. the water vascular system, 

 the perivisceral fluid and the blood system. 



25. RESERVE SUBSTANCES IN ECHINODERMS. 



It has frequently been assumed in the previous chapters that 

 the Echinoderrns live from day to day, so to say, resorbing 

 with surprising rapidity everything that comes into their peri- 

 visceral fluid and constantly starving and hunting for food. 

 For this reason it seemed desirable to make sure whether they 

 are perhaps in the possession of many reserve substances available 

 under such circumstances. 



As far as the fatty reserves are concerned, I made some 

 experiments in order to ascertain whether fats do occur at all 

 in the starfish and, if so, in what quantities. I made these expe- 

 riments for a double purpose, in the first place for the reason 

 mentioned above, in the second place however in order to eluci- 

 date the question of the digestion of fats, discussed from another 

 angle in a special chapter. The presence of fats in certain animals 

 of course, as stated before, does not necessarily prove the pre- 

 sence in them of sieatolytic enzymes, these may be derived from 

 other sources, from carbohydrates or even from proteins. But 

 nevertheless it makes their presence more probable. 



In order to determine the quantity of fats present in one 

 starfish, I extracted two specimens with a mixture of alcohol- 

 ether. The arms of one specimen and its disc suspended in a 

 filter-paper cone, were extracted in a soxhlet till the extraction 

 fluid was watery clear, after this another specimen was treated 

 in the same way. 



The liquid thus obtained appeared to contain a large quantity 

 of pigment. Not all the pigment was dissolved away from the 

 animal though, a small quantity seemed to be deposited in some 

 way in the calcarous skeleton. In to get rid of the pigment, 

 the liquid was boiled for some time with charcoal, then filtered. 

 The charcoal was again extracted with cold ether, this ether 

 was added to the rest of the extract; the treatment was then 

 repeated, again with a fresh quantity of charcoal. 



By repeating this procedure numerous times I succeeded in 

 getting rid of all the pigment. Whether or not lost any fat, 

 I do not dare to decide, but it does not seem to me probable. 



The liquid was now gradually evaporated in a large watch- 

 glass over a water-bath. The residue which did not seem to 



