NATURAL HISTORY SOCIETY OF GLASGOW. 23 



takes place around the perforation, and on the flattened side; (3) 

 an irregular or contorted state of the restored portions is frequently 

 to be observed. The deduction drawn by a " Corresponding Member " 

 appears to be that, although admitting this appearance may be 

 affected by the loss of a side-arm, and consequent repair of the 

 injured parts, the chief reason is that of disease, arising "from an 

 overstrain caused by forced flexion, or from idiopathic causes." 

 He says: "Recalling to mind the phenomena attending necrosis, or 

 caries, or even fracture, when defensive action is active, as well as 

 the more rare instances of adventitious structure, formed to defend 

 or support certain organs of animals against threatened destruction, 

 and dismissing the idea of wound or puncture, how does the 

 question rest?" 



Freely admitting, as T do, that solitary instances of disease might 

 be found and demonstrated amongst fossil Crinoidea, and again as 

 freely admitting that the appearances under discussion are occa- 

 sionally caused by the loss and repair of a side-arm, I cannot, at 

 the same time, subscribe to the theory of disease so ably and in the 

 sense advocated by a " Corresponding Member." The reasons for 

 this difference of opinion will be found in the following descriptions 

 of specimens — suffice it to say that I believe, with the exception 

 of rare cases, the puncture and swellings visible on the majority of 

 Crinoid stems are produced by a series of causes exterior to the 

 will of the Crinoid, usually in the form of other organisms using 

 the crinoid -structure as a means towards their own existence. 

 Neither will strained flexure account for the phenomena, for it is 

 now known that the stems of the Crinoidea will undergo this to 

 an enormous extent without injury. 



1878. — I am indebted to the kindness of my friend, Dr. J. R. S. 

 Hunter, of Braidwood, for the loan of a second pamphlet by the 

 same " Corresponding Member" — "Notes and Observations on In- 

 jured or Diseased Crinoids, &c."* — in which a still more elaborate 

 and interesting array of facts are set forth. Several swollen 

 examples of Crinoid stems are described, but do not now call for 

 any special remark, except that the enlargement appears to be 

 frequently accompanied by a straining of the stem. By far the 

 most interesting portion of this communication is that on "Adven- 

 titious Structures on Crinoidal Fragments," in which is shown the 



*Proc. Nat. Hist Soc. Glasgow, 1878, III., pt. 3, p. 333. 



