66 



In the Holothurians we find that the body wall is simply 

 a sac in which the gut is folded many times. The urchins are 

 also simple, round containers and even here the gut shows two 

 curvatures and winds around in every direction. But in the 

 starfishes it would not be possible for sufficiently large quan- 

 tities of food to reach the tips of the arms on account of the 

 lack of circulation, if the gut did not extend into these arms. 

 The „Mitteldarmdivertikel" are a logical postulate here. 



These middle-gut sacs are on the one hand a place of enzyme 

 secretion, but on the other hand, chiefly organs of resorption. 

 The first authors who clearly realised this important fact, were 

 Biedermann and Moritz 9) in their almost classical monograph 

 on the function of the so-called „liver" in molluscs. They 

 showed that the anatomical relations are such that the food 

 is forced to enter into the „liver" up into the smallest rami- 

 fications. This can easily be shown, if e. g. the animals are fed 

 on flour and the iodine test is applied to microscopical sections. 



Numerous structures which have always been a puzzle to 

 anatomists and on which a very particular light is thrown by 

 this discovery, have since been explained by it. Two very inte- 

 resting cases have been described by Jordan 64). 



In case this „liver" is not present, i. e. in those groups to 

 which the collective name of ..injecurata" has been given, other 

 devices take their place in such groups as have an insufficient 

 circulation. In this way the ramifications of the gut of the 

 flatworms, the coeca of Aphrodite, the curvatures in the digestive 

 tract of sea urchins and sea cucumbers etc. may be explained. 



It has frequently been stated that bile pigments are found 

 in these livers. This is not true and later authors (Hoppe- 

 Scyler, Frenzel, Plateau, Voit, Fredericq et al.) 

 always failed to find them. 



Summarising this brief introduction we may say that these 

 middle-gut sacs and the liver of the vertebrates have no specific 

 function in common. These so-called livers are nothing but 

 extensions of the middle-guts for the function of resorption, a 

 system of blind-guts. 



From the very beginning of this work I suspected that the 

 radial sacs of the starfishes would appear to have that same 

 function. To get some more definite information on this question 

 I used different procedures partly of a positive, partly of a 

 negative nature. 



Two different views have been held in the past; they were 

 either considered to be organs of secretion or organs of resorption. 

 The first view is the one held by nearly all authors f.i. Grif- 

 fiths, Frenzel, Fredericq, Krukenberg, Cuenot (in 

 1887) and others. Biedermann in Winterstein's Handbuch, 

 summ'arises the earlier views thus : „dasz die Radialanhange des 



