INTRODUCTION. 



Trotz der bedauerlichen UnvoUstandigkeit unserer 

 Kenntnisse uber die Ernahrung der Echinodermen bietet 

 doch schon das wenige was bisjetzt dariiber festgestellt 

 ist, ungewohnliches Interesse dar und laszt weitere 

 Untersuchungen hochst wunschenswert erscheinen. 



Biederraann in Winterstein's Handbuch. 



More than anything else perhaps the young science of com- 

 parative physiology needs systematic work, in which the old 

 literature is taken into consideration, but where the results are 

 controled and verified by newer and often times better methods. 

 This literature is on account of the fact that in the last 35 years 

 biologists have almost exclusively been specialising on compara- 

 tive anatomy and related sciences, in most cases either very 

 old or very recent. The old literature, for a large part French, 

 contains unknown treasures, but is frequently difficult to find. 

 Many of the older papers will prove to be completely untrust- 

 worthy, be it because the methods are no more up to date, 

 be it because the writer, not thoroughly acquainted either with 

 chemistry or physics or with the anatomy of the group studied 

 — the latter is often the case with work of medical physiolo- 

 gists — has made more or less fundamental mistakes. 



This work must not only consist of a ,.Nachprufung" of the 

 work of previous authors and its appreciation, but also in a 

 supplementing of those parts in which our knowledge is still in- 

 complete. If all comparative physiologists work together in this 

 way, we will in a short time have a basis from where to start, 

 we will have formulated our problems and will be able to 

 explore new fields more fruitfully than this has been done till now. 



Ideas like these have induced me to study a problem Uke : 

 Digestion in Echinoderms, a little more closely. 1 do not claim 

 that my work contains an answer to burning questions or is 

 concerned with such problems as occupy the modern biological 

 mind, but as „clearing work" it may have some value. 



The study of one definite group more in detail is especially 

 desirable because other relations and other functions can be 

 studied at the same time, so as to give a clear picture of the 

 whole process of food intake, digestion, metabolism, excretion 

 and respiration, a view of a definite complex of functions of 

 the animal machinery. The whole literature contains an abundance 

 of single facts, but real problems as there are hundreds, have 

 seldom been attacked. 



