439 



The Kegenerated Scales of Fijndulus Heteroclituus Linne' 

 WITH A Preliminary Note on Their Formation. 



By Will Scott. 



The work of Hoffbauer, 'UU, on the scales of the cari) established the 

 fact that, lip to the third year, tlie ase of tliis tisli could be determined l>y 

 the sculpture of tlie scales. Jolmston 'Or>-'08-'10 has shown that not only 

 can the age of the salmon be detennined by the sculpture of the scale, but 

 the emigration of the young salmon (parr) from river to sea and each 

 return to spawn of tlie sexually mature leave an indelible mark upon the 

 scale. These marks have been rendered perfectly intelligible by the work 

 of .Johnston and that of his associates on the Scottish fisheries board. 



Hutton, "10, in working on the scales of the Wye River salmon ob- 

 served, occasionally, scales quite different from the normal ones and sug- 

 gested that these scales might be the result of regeneration. If this sug- 

 gestion be true then it would be possible, by scale ex.amiiiatioii, to deter- 

 mine the wounds received by and. in a general way, the hazards encount- 

 ered by any individual. To add this additional index to the life history of 

 a tish these experiments concerning tlie regenerated scale were performe<l. 



1'he Killifish, I'undulus heteroclitus Linne, was selected for the experi- 

 ment because of its abundance and its well known hardiness. Many fish 

 of this species, at this season of the year (Aug.). were infected with a 

 sjiorozoan parasite. This infection proved fatal in most cases, conse- 

 quently great care had to be exercised in selecting material. The opera- 

 tion consisted in the removal of about six rows of scales from the left 

 side between the po.sterior end of the dorsal fin and the anal fin. The 

 fish were co\'ered with clean cheese cloth which was kept wet with sea 

 water ; only a small area was exposed at any one time. The scales were 

 lifted from their pockets with a scalpel, care being taken not to injure 

 the inner wall of the pocket. If the circulatory system was injured in any 

 noticeable degree sporozoan infecti(ni occurred. 



- The work was done while acting as scientific assistant in the laboratory of 

 the IT. S. Fish Com. at Woods Hole. Mass., and is published with the permission 

 of the Hon. G( o. M. Bowevs, Commissioner of Fisherie.s. 



