M. E. Storms on the Adhesive Disk o/'Echeneis. 69 



3. G. Beck*, after describing and naming the different 

 elements of the disk, considers the pectinated lamella; to be 

 enlarged spinous rays and ascribes the two other elements to 

 the iuternem-al bones [Flossentrager) . 



4. Finally, M. Niemiect finds it impossible to explain the 

 homologies of the lamellse composing the disk. 



In order to arrive at a satisfactory solution of these ques- 

 tions it will be necessary: 



1. First, to examine attentively the different elements of 



the disk ; 



2. Secondly, to study the structure of a normal spinous 



dorsiil fin ; 



3. Lastly, to compare both organs together. 



I. Description of the Elements of the Disk. 



Two kinds of structures may be regarded as entering into 

 the com position of the hard parts of the disk : — 

 1st. Structures which have a dermal origin ; 

 2nd. The skeleton properly so-called of the disk. 



1. To the first category belong the rows of small teeth 

 which cover the posterior margins of the lamella. That they 

 are not formed by outgrow^ths of the bony substance of the 

 laraellffi is proved by the facility with which they fall off by 

 prolonged maceration or ebullition. The presence of these 

 rows of teeth on the posterior margin of the lamella was one 

 of the reasons which prevented Ur. Kner J from adopting the 

 usual interpretation of the disk of Echeneis. 



2. The properly so-called bony skeleton of the disk. 



A. A typical segment of the disk is composed of three 

 elements : — 



a. The interneural ray ; 



^. The intercalary bone [Fussjalatt, G. Beck ; Os traUcu- 

 laire^ Niemiec) ; 



7. The pectinated lamellge {Zdhnplatten oi Gr. Beck ; Lames 

 pectinees of Niemiec). 



a. Interneural ray. — This bone is rather small and has 

 pretty much the usual form, the principal difference being 

 that the upper part, which expands to carry the ray, is in the 

 same plane as the lower blade ; this is caused by the direction 



* G. Beck, « Ueber die Haftsclieibe der Echeneis remom,'' Inaugural 

 Dissertation, 1879, p. 31. 



t Niemiec, " Les ventouses dans le regne animal," Recueil zoologiciue 

 Suisse, tome ii. 1885, p. 117. •. 1 • 



\ Dr. E. Kuer, " Ueber den Flossenbau der Fische," Sitzungsb. kais. 

 Akad. Wiss. Wien, Bd. xlii. p. 7G8. 



