NO. 1846. ON CERTAIN ELEUTHEROZOIC PELMATOZOA—KIRK. 61 



was a colony of adult Eucalyptocrinus, the members of which for some 

 reason or other, became detached and left this immediate locahty. 



It must necessarily follow upon the death and decay of a crinoid 

 that residual roots or basal disks are left and many roots referable 

 to adult specimens may no doubt be assigned to tliis category. The 

 vast number of immature disks which are to be found can not, I 

 thmk, be explained on this basis, however. Again, in the case of 

 detachment for this reason, there would be no sign of resorption at 

 the Ime of separation, such as is indicated in many examples. This 

 point is equally effective against the hypothesis of violent disruption 

 in such instances as it is to be observed. Even were there no signs 

 of resorption at the point of detachment these basal disks need by no 

 means be considered as having been left by the death and decay of 

 the animals. Disruption of the column may well become effective 

 elsewhere than at its juncture with the base. Indeed from the little 

 we know in regard to such matters it appears that the separation of 

 the column occurs w4th great frequency at higher points. Subsequent 

 to such a type of detachment, which on the whole I think we may con- 

 sider, as a rule, involuntary, the residual columnals will become disar- 

 ticulated and leave a base with a sharply defuied stem cicatrix. 



In connection with these residual disks should be recalled those 

 spirally coiled columns noted above under the discussion of Glypto- 

 crinus. In these specimens the distal portion of a stem has been 

 spirally wound about the column of another crinoid, in many cases 

 being laid on as neatly as thread upon a spool. Subsequently, a 

 fusion has taken place between the two columns resulting in the abso- 

 lute fixation of the attaching organism. Most of the stems attached 

 in this manner indicate that as in the case of Glyptocrinus, the crinoids 

 were comparatively young forms, and became detached later in life. 



It must be granted that those forms in which the distal portions of 

 the columns do not bear roots or disks of cementation were not firmly 

 affixed to the bottom. Furthermore, those types ha^^^lg cirri obvi- 

 ously adapted for grasping or in which there is a very considerable 

 development of the cirri, may be considered to have led an eleuthero- 

 zoic existence. It seems possible to carry this postulate of a free 

 existence among the stalked crinoids still further. In other words, 

 it seems quite probable that many crinoids having rootlets were never 

 permanently attached. This reference is made from conditions as 

 we have them in the preservation of crinoids in the colonies of paleo- 

 zoic times. 



Were the crinoids to have been tnily rooted, the distal portion of 

 the stem must of necessity have been buried in the material composing 

 the bottom. Upon the death of such forms it is obvious that without 

 very considerable disturbance of the sediment surrounding these 



