A MONOGRAPH OF THE EXISTING CKINOIDS 67 



Comissia parvula shows for a comasterid an abnormally high figure, partly because 

 it is a small species, partly because it is endocyclic, and partly because it is a deep- 

 sea species. For the last-mentioned reason the figure for Catoptometra magnified, minor 

 is also unusually high. Lamprometra palmata is a littoral type and therefore shows 

 a low figure. Species having a high specific weight, that is, strongly calcified 

 species, usually show low figures also. In Pectinometra jlavopurpurea the decrease is 

 counterbalanced by the great depth at which the animal is found. On the other 

 hand, the slightly calcified Antedon petasus and Cyllometra pulchella the latter also 

 very small show very high figures. 



Gisle"n said it is more difficult to explain the deviation in Tropiometra afra macro- 

 discus and Heliometra glacialis. Both are, however, exceptionally large types, and 

 the former is at the same time a littoral species. The body of Heliometra glacialis 

 is not very strongly calcified, which should perhaps counterbalance its gigantic size, 

 and so also should the fact that it is not a littoral form. 



An analysis of the intestinal contents of Heliometra glacialis showed a great 

 abundance of copepods, these being present almost exclusively very nourishing food. 

 Tlu's comatulid lives outside the great glaciers of Spitsbergen and Greenland, where an 

 abundance of plankton is found. Gisl4n suggests that possibly this may explain 

 to some degree the low figure. The appearance of "rudimentary combs" on the 

 proximal pinnules must, however, be noticed. 



Gislen noted that he had chosen for his investigations the most divergent types from 

 the most diverse localities he was able to obtain, and he said that therefore one should 

 not feel too much surprised if a few divergencies from the general rule appear. It is 

 possible that in the two cases of great divergency described some unknown facts may 

 play a part. Taken as a whole, however, it seemed to Gisl6n that the difference 

 between the low figure of the Comasteridae and the high figure for the rest of the 

 comatulids is very remarkable. It is all the more noticeable that the figures given 

 for the Comasteridae are low throughout, as three of the five comasterids examined 

 have ambulacra! furrows on all the arms and most of the pinnules. 



FORMATION AND CONTENTS OF THE INTESTINE IN THE COMASTERIDAE 



Gisle'n noted that although in the Comasteridae the ambulacra! grooves are 

 abnormally short in proportion to the size of the animals, the great length of the 

 intestine suggests that the food is richer and at the same time more difficult to digest. 

 He said that the author's explanation of the elongated digestive tube in the Coma- 

 steridae (Part 1, p. 343, fourth paragraph) is only in part correct. Certainly the 

 Comasteridae in general are shallow-water types, particularly the exocyclic ones; 

 but so also are certain families with central mouths, as the Himerometridae, Maria- 

 metridae, Stephanometridae, and Tropiometridae. That the Comasteridae are 

 confined to muddy bottoms is not correct, as may be seen by an examination of the 

 localities given in the Siboga report. Comasterids were collected at 65 localities at which 

 the character of the bottom was recorded; of these localities 54 also yielded exocyclic 

 comatulids. In 41 of these localities they were taken from a bottom consisting of 

 stone, sand, "coral," and Lithothamnion; mud was found in only three cases. GisleVs 

 examination of the intestinal contents in the Comasteridae showed that the vegetable 



