42 PROCEEDINGS OF THIE NATIONAL MV8EVM. vol. 4l. 



informed by Doctor Yatsu, of the University of Tokio, that the 

 fishermen in laying out their lines in a given direction seldom if ever 

 bring up specimens of Metacrinus. On the other hand, lines laid out 

 at right angles to this direction frequently brmg up specimens. 

 This fact the fisherman explains by assuming that the crinoids are 

 aligned in long courses which are some distance apart. When the 

 tackle is laid out parallel to these Imes, few crinoids are taken, but 

 when laid across them, the conditions are more favorable. When the 

 great length of these set lines is considered, for I have been told that 

 they are at times a mile or more in length, it does seem surprising 

 that were the crinoids restricted to large roughly circular areas, lines 

 set in one direction would not be quite as apt to entangle specimens 

 as those set in another direction. 



A semilinear arrangement of small colonies rather than an approxi- 

 mately radial one is perhaps not wholly in accord with current ideas 

 relative to the distribution of the crinoids, but the facts as given by 

 Doctor Yatsu are at least worthy of consideration. It is possible 

 that such a Imear arrangement might be voluntarily assumed as 

 directly affecting food supply. For instance, rows of crinoids at 

 right angles to a current would have a far better food supply than 

 closely segregated groups of individuals. On the other hand, such 

 a linear arrangement of the crinoids may well bear a direct relation 

 to the bathymetric range of the animals. 



Evolution of the Pentacrinidse. — The evolution of the Pentacrinidse 

 may only completely be worked out with the aid of extensive collec- 

 tions of the fossil representatives of the family. As indicated by 

 Bather (1900) we have in all probability to start with some such 

 type as Dadocrinus. We next have Holocrinus where the appearance 

 of verticils of cirri is to be noted. The next stage is one that is more 

 distinctively like the typical members of the family, and perhaps is 

 represented by Balanocrinus. From such stock at least two divergent 

 lines may be held to have arisen. One line — that characterized by 

 Pentacrinus — is comparatively short lived and terminates with the 

 group of species characterized by P.fossilis (briareus). On the other 

 hand, we have the line that for a considerable period was no doubt 

 made up of forms essentially similar to Isocrinus in structure. From 

 this line probably are to be derived the modern representatives of the 

 family. 



Having demonstrated the widespread occurrence of a free existence 

 in the case of certain living Crinoidea and their comparatively recent 

 fossil representatives, it will be interesting to note similar uistances 

 of a detached mode of life among the Paleozoic forms. Only those 

 cases will be given at this time that are of unquestioned standing. 

 Subsequently, in the general treatment of eleutherozoic conditions 

 as they appear to have obtained among the paleozoic Crinoidea, 



