NATURAL HISTORY SOCIETY OF GLASGOW. 93 



and the column so connected and so placed would have ample 

 play, without jar or arrest, and would apparently be the chief 

 source of defence or protection from injury from without. 



For the purpose in view no other part of the animal need be 

 noticed. 



Impressions are frequently stamped on the columns, made in 

 all likelihood after deposition; and fragments depressed irregularly, 

 without fracture, are often collected, showing that the parts of 

 the column were, so far, soft and ductile. " Wounds " or 

 ''punctures" were consequently possible. But judging from 

 analogy, the system would, in the event of a wound or puncture, 

 direct the restorative matter to, or towards the injured part, not 

 away from it, as observed in these tumid parts of columns. The 

 same remark applies to a side-arm broken off. An arm has joints, 

 and a central canal, as in the primary column; but junction of the 

 column and side-arm is only by a peculiar articulation to the 

 outside of a column without weakening it, the canal being carried 

 on to the central one by a transverse passage through the body of 

 the column till it joins the main central cavity. If, then, a side- 

 arm were loped off at the articulation or elsewhere, the restorative 

 process would be directed to the injured, and not to any unin- 

 jured part ; in all instances, nevertheless, the protecting fortifica- 

 tion is not direct. 



Now, what little remains to be stated would perhaps be better 

 done if strictly demonstrative. 



Any description of these swelled columns of Crinoidea — not 

 confined to Poteriocrinus crassus alone, by the way, but extending 

 to several species, points only to one marked feature, a cylindrical 

 tumidity or swelling, one side of which is depressed and perforated 

 in a column which above and below the swelling is in a normal 

 condition. But there are many varieties or stages of this morbid 

 or diseased condition. Among 28 specimens specially examined, 

 some have been selected as modifications of each other, from the 

 stage of active diseased action to something like restoration of 

 parts — all teaching one lesson. 



Two specimens, something like Avhat Miller describes, namely, 

 several joints bulging out on three sides, the other depressed with 

 an irregular circular hole with inverted edges in the centre of the 

 depression, the column above and below being in a normal state. 

 Bulging as long as wide. 



