72 M. R. Storms on the Adhesive Disk o/"Eclieneis. 



This homology of the pectinated plates and spinous rays 

 being admitted, there still remains to explain the way in 

 which a spinous ray has been transformed. 



Three methods have been suggested : — 



I. The fin-rays have been bent downwards on both sides 



(Voigt *j Blainville f, according to Dr. Giinther) . 



II. Each pair of lamellai is formed out of one spine, each 



half of which is bent down towards the right and left 

 (Dr. Giinther I). 



III. Each pair of lamellaj represents a transversely enlarged 

 spine (G. Beck§). 



I. The^rs^ hypothesis must be rejected, because the pecti- 

 nated lamel]a3 are in pairs which correspond to each other 

 and are supported by a single interneural. 



II. The second notion seems very improbable, 1. Sup- 

 posing such a splitting and bending down of the two 

 halves of a spinous ray to have taken place at first acciden- 

 tally (teratologically) , how could such an accidental struc- 

 ture have been immediately seized upon and adapted to a new 

 hal)it ? 2. A dorsal fin split in half does not by itself form an 

 adhesive disk. 3. Then how could the exterior extremities 

 of the lamellae, which in this supposition represent the points 

 of the spines, be as firmly united to the connective tissue of 

 the integuments of the head, as they appear to be, according to 

 M. Niemiec || ? 4. And finally, if we take two corresponding 

 pectinated lamellce, and if we replace them in their supposed 

 primitive position, it can be seen immediately that the pro- 

 cesses corresponding to those of a normal spinous ray are 

 then situated on diametrically opposite sides, in the spinous 

 ray and in the pectinated lamella. 



III. The i/ii9'd supposition, which maintains that the pecti- 

 nated lamellse are transversely enlarged spines, avoids the former 

 difiiculties ; but there remains still to be explained in what 

 way the enlargement took place. To suppose that the spine 

 proper of the spinous ray took part in the enlargement would 

 be very difficult to understand and quite unjustifiable by 

 observation. There is no trace on any of the lamellge of what 

 might represent such an enlarged spine. It is much more 

 natural to think that the bases of the spinous rays alone have 

 foimed the lamellse and that the spine proper was gradually 

 reduced in size until it has nearly disappeared. Such a reduc- 



* Giintlier, Ann. & Mag. Nat. Hist. [3] 1860, vol. v. p. 389. 



t Id. ibid. 



I Giinther, ' The Study of Fishea,' p. 460. 



§ Beck, loc. cit. p. .^1. 



y Niemiec, he, cit. p. Hit. 



