REGENERATION IN FUNDULUS HETEROCLITUS. I 5 



peared over the cut end of the spinal cord. This fish was kept 

 under observation for three months but during this time the 

 white knob did not increase perceptibly in size. As far as external 

 examination could determine no regeneration of bone took place. 



PECTORAL AND PELVIC FINS. 



On October 25, 1905, twenty-four fish had their right pectoral 

 and left pelvic fins removed. The cuts were made as close to 

 the body as possible. In three months all died but three. These 

 showed no regeneration of the pectoral fin but in one case a slight 

 indication of a regenerating pelvic. Two weeks later two of these 

 were still living, both showing the regenerating pelvics well under 

 way and a well-defined indication of regenerating pectorals. 

 Unfortunately the two fish died a few days later. Another set 

 of twelve fish were cut in the same way but all died within a 

 month, showing no signs of regeneration. 



A third set of twenty-five fish cut as above, were started 

 on February 16, 1906. Nine weeks later eighteen were still 

 living ; five of these showed regenerating pelvics and one, an 

 indication of regenerating pectoral ; the rest no regeneration 

 of either fin. Two weeks later (at the time of writing) seventeen 

 were living. Two of these showed regenerating pectorals dis- 

 tinctly, in the shape of a small knob of tissue which no doubt 

 contained two or three regenerating rays, since the fish moved 

 the structure to and fro like a fin. Eight of this same lot were 

 regenerating their missing pelvic fins, the new structure in some 

 cases being one eighth of an inch long. 



An examination of the direction of the cut in the removal of 

 the pectoral fins shows that in most cases all the dermal fin rays 

 are removed entire, i. e., disarticulated. Occasionally, however, 

 the cut does not completely remove the uppermost one or two 

 rays. These rays extend inward a little further than the others 

 and so their proximal stumps may remain in situ and give rise to 

 little pointed structures as described above, but never to a com- 

 plete fin. In the case of the pelvic fins, it is not possible as a 

 rule to cut them so close in ; thus it more frequently happens 

 that stumps of the rays are left, sometimes a few, sometimes all. 

 Regeneration takes place from the cut ends of these only. 



