MONOGRAPH OF THE EXISTINU CKINOIDS. 749 



The acid solution of pentacrinin when slowly evaporated and concentrated 

 yields a precipitate, which, when collected and dried, appears as a dark violet 

 amorphous powder. This substance, viewed by transmitted light as adhering to 

 the filter paper and rendered transparent with glycerin, yields the same spectrum 

 as the acid solution. The dried coloring matter is very sparingly soluble in abso- 

 ulte alcohol, but freely soluble in this on the addition of a few drops of hydro- 

 chloric acid. It is not soluble in dilute hydrochloric acid alone, requiring the 

 addition of alcohol to show the spectrum. 



The fresh coloring matter is soluble in fresh water, but remains partly sus- 

 pended, forming a slightly opaque dark purple solution, which gives, when quite 

 fresh, a mixed acid and alkaline spectrum. When the aqueous solution is acidified 

 the coloring matter becomes entirely dissolved and the fluid becomes clear and 

 transparent and of a beautiful pink, yielding the same spectrum as the acidified 

 alcoholic solution. When the intense watery solution is rendered alkaline a green 

 flocculent precipitate is formed, and in a very intense solution the two outer bands, 

 the most refrangible and the least refrangible, are lost, being encroached upon and 

 included in the general absorption of the ends of the spectrum. 



All the specimens obtained off the Kermadec Islands (representing Hypalo- 

 crinus naresianus, Metacrinus nodosus, and M. ivyvittii) were of a uniform dusky 

 purple when brought to the surface, being evidently colored by acid pentacrinin. 



The specimens secured off the Meangis Islands represented seven species 

 (Endoxocrinus alternicirrus, Hypalocrinus naresianus, Metacrimts costatus, M. 

 moseleyi, ?M. murrayi, M. varians, and M. wyvillii). Of these, three (Metacrinus 

 costatus, M. variant, and M. wymllii} were similarly colored uniform dusky purple, 

 one being especially dark, while one (Hypalocrinus naresianus) was of a light 

 pinkish red and did not contain purple pentacrinin at all. 



The specimens dredged off the Kei Islands (representing Metacrinus angulatus, 

 M. cingulatus, ?M. murrayi, M . nobilis, and M. tuberosus) when fresh had their 

 stems almost white and their crowns light yellow or light reddish orange, showing 

 no purple coloration at all. 



Those obtained off Panglao and Siquijor (f/^nJoxocrinus alte-micimis, 

 f Hypalocrinus naresianus, and f Metacrinus murrayi) were almost colorless; never- 

 theless, when placed in alcohol they yielded a solution which was deeply colored 

 sap green and which, when acidified, became of the usual deep pink of pentacrinin. 

 Thus in these examples the pentacrinin, though present in great abundance, was 

 entirely masked. 



It is possible that these specimens would have shown an alkaline reaction in 

 the fresh condition. Unfortunately the test was not made. The pentacrinin would 

 be far less visible in the green alkaline condition. 



Red pentacrinin. Hypalocrinus naresianus gave a simple light red solution in 

 absolute alcohol. This solution, when very intense, absorbed all the spectrum 

 except a band of light between E and B. When the solution was weaker it showed 

 a single broad band in the region of E, b, and F, with some absorption of the ends 

 of the spectrum. Addition of ammonia reduced the brightness of the color of the 



