REGENERATION OF CERTAIN STRUCTURES IN 

 FUNDULUS HETEROCLITUS. 



C. V. MORRILL, JR. 



It is a fact of common knowledge to all observers of fish kept 

 in aquaria, that portions of the fins, lost through accident, or pur- 

 posely removed will be replaced by new structures which cannot 

 be distinguished, in many cases, from normal fins. This ability 

 to regenerate has been examined by Duncker (1905), Morgan 

 (1900, 1902), Nussbaum and Sidoriak ( 1900), Mazza (1890) and 

 Broussonet (1786). The following experiments were made to 

 test the effect of cutting off the fins close to the body. The 

 regenerative powers of the operculum, the lower jaw, the scales 

 and the lens were also tested. 



The various sets of experiments described below were tried on 

 different fish, no one fish having more than one fin removed, 

 except in the case of pectorals and pelvics which were removed 

 from the same fish, the right pectoral and left pelvic being always 

 selected for convenience. 



I wish to express my thanks to Prof. T. H. Morgan, who 

 kindly suggested this problem and under whose direction it was 

 completed. My thanks are also due to the staff of the New York 

 Aquarium, and to Dr. F. B. Sumner, director of the U. S. Fishe- 

 ries Laboratory at Wood's Hole, Mass., who kindly placed the 

 necessary tanks and fish at my disposal. 



DORSAL FIN. 



On October 10, 1905, eighteen fish had the dorsal fin cut oft 

 as close to the body as possible. These were examined from 

 time to time until December 29, 1905, when due to various 

 causes, principally fungal growth, the number had become 

 reduced to thirteen. All of these with one exception were 

 regenerating a new fin. The excepted case was kept under ob- 

 servation three months longer but at the end of that time, 

 twenty-six weeks after operation, it had developed only a small 



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