439 



*The Regenerated Scales of Ftindulus Heteroclituus Linne' 

 WITH A Preliminary Note on Their Formation. 



By Will Scott. 



The work of Hoffbaiier, '99, on the scales of the c-lrp established the 

 fact that, up to the third year, the age of this fish could be determiued by 

 the sculpture of the scales. Johnston 'Oo-'08-'10 has shown that not only 

 can the age of the salmon I)e determined by the sculpture of the scale, but 

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

 return to spawn of the 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 examination, 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 fish these experiments concerning the regenerated scale were performed. 



The Killifish, Fundulus heteroclitus Linne, was selected for the experi- 

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

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

 sporozoan 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 posterior end of the dorsal fin and the anal fin. The 

 fish were covered 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 infection occui'red. 



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

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

 of the Hon. Geo. M. Bowers, Commissioner of Fisheries. 



