REGENERATION IN FUNDULUS HETEROCLITUS. I 3 



new growth. Six weeks later the regeneration was fairly started 

 in five fish which still survived. These five were examined one 

 week later, i. c., sixteen weeks after removal of the fin and it was 

 found that three showed slight regeneration while the other two 

 had a new fin about half the size of the original one. In these 

 last, the fin was normal in shape and position, though small, and 

 the rays parallel to one another as in the old fin. Ten weeks 

 later, twenty-one weeks after removal of original fin, the regen- 

 eration was almost complete, the new fin having the normal 

 number of fin-rays and being scarcely distinguishable from ordi- 

 nary anal fins. 



Here as in the case of the dorsal fin, the cut usually passes a 

 short distance distal to the articulation of the dermal with the 

 bony fin rays. But it may pass a little further in through the 

 articulations if not carefully made, as the body is soft in the 

 region of this fin. A cut of this kind results, as might be ex- 

 pected, in no regeneration. The cut may, however, pass through 

 the articulations of some rays and the shafts of others ; then the 

 new growth takes place from the cut ends of the latter only, 

 producing an irregular structure with less than the normal num- 

 ber of fin-rays. 



The external prolongation of the oviduct in the females, which 

 passes down the anterior end of the fin is, of course, severed 

 with the fin. It regenerates, as might be expected, only when 

 the anterior fin-ray which supports it, regenerates, not otherwise. 



CAUDAL FIN. 



On October 5, 1905, the caudal fins were removed from 

 eighteen fish, the cut being made in a curve so as to remove the 

 entire fin, without at the same time cutting off any of the tail 

 vertebrae proper. This operation is rather severe ; there is 

 usually some bleeding and the edges do not close over the 

 wound very readily. In consequence the number of fish lost is 

 usually considerable. After twelve weeks, five fish only re- 

 mained, all showing regeneration of the fin to some extent. Two 

 weeks later the regeneration was still proceeding slowly but 

 somewhat irregularly, the new fin-rays being bent downward, 

 forming a considerable angle with the original horizontal direc- 



