body wall, animals of 15 c.M. eventually are as short as 

 6 — 1 c.M. Numerous small tube feet are found scattered all 

 over the surface of the body. Except for the enddiscs of the 

 tube-feet no calcareous bodies are found, according to S e 1 e n k a. 

 Ay res finds numerous long plates with a kind of crown in 

 the middle. The members of the calcareous ring are fused 

 together completely. Five calcareous teeth are found in the 

 anus. The behavior of this species has been described in detail 

 by Pears e 98). 



In Bermuda I had occasion to study Stichopus moebii. 

 Semper, a flat and very large aspidochirote Holothurian. It 

 has 18 gray tentacles; on the back only very few tube-feet 

 are found. One Polian vesicle and one stone-canal are present. 

 Its color is reddish-grey with black spots in the West-Indian 

 specimens — one on a hundred specimens in the Bermuda-islands 

 also has this coloration ~~, absolutely black in most of the 

 Bermuda specimens. Very strong calcareous elements are fouiid 

 in the tube-feet. 



3. ANATOMICAL DETAILS ON THE 

 DIGESTIVE TRACT '). 



Related as the Echinoderms may be in anatomical respect 

 (..This is one of the best characterised and most distinct Phyla 

 of the Animal Kingdom." Ray Lankester) by their penta- 

 gonal symmetry, by the structure of their body cavities and 

 by their larval forms, physiologically there is a big difference. 

 The feeding habits are widely divergent in the different groups, 

 as will appear from the short descriptions, given in the next chapter. 

 Stichopus eats calcareous sand; Thyone, other cucumbers and 

 the crinoids catch small planctonts; the starfishes are the vora- 

 cious carnivores of the group; the urchins the rodents. Such 

 differences must give rise to big differences in morphological 

 respect and in fact the digestive tract is, at least as far as the 

 macroscopical anatomy is concerned, almost entirely different 

 in the various groups. 



In the starfishes the organs of digestion have a very peculiar 

 structure. This is on one hand due to their „external digestion", 

 which will be described in the next chapter, on the other hand 

 to their peculiar star-like shape. It consists chiefly of a large, 

 strongly muscular ..stomach" in the disc and of the ..radial 

 sacs" or ..pyloric coeca". which usually lie in pairs ^) in the 



■) This chapter does not pretend to be complete. It is beyond the scope of 

 the present paper to give such account ; the interested reader can iind enough 

 details in the numerous papers of Hamann 50), 51), and 51^), of Tiede- 

 mann 127), Frenzel 41), Jourdan 71) and 72), Koehler 74), Prouho 

 103) and others. A good key to this literature is found in 140). 



') In some cases — probably on account of mutilations — I found three of 

 these organs present in one arm. 



