68 SALMON AND TROUT IN ALASKA. 



Jordan " reiterates essentially the same statement, and this belief 

 was held also by Weismann. Thomas Hunt Morgan has by experi- 

 ment demonstrated a slightly greater power of regeneration of lost 

 extremities of fins than had previously been held to exist. After 

 amputation of the distal portions of the caudal in the mudfish {Fun- 

 dulus heteroclitus) regeneration was distinctly marked in from seven to 

 twelve days, indicating the ultimate reproduction of a perfect fin. In 

 further experiments both the paired and median fins of this fish were 

 found to possess the power of reproducing the distal portions after 

 amputation. Similar regeneration in the caudal was demonstrated 

 in the common scup {Stenotomus chrysops) and the mackerel shad 

 {Decapterus niacarellus) . The presence of this fin-regenerative po- 

 tency was also noted in the kingfish ( Menticirrhus saxaiilisC^j) ), the 

 goldfish (Carassius auratus), a minnow (probably a Leuciscus) , the 

 stone cat {Notunts sp.), and others. In a spiny-rayed labroid 

 (Ctenolahrus) a pectoral fin cut off at the middle regenerated com- 

 pletely, and a pelvic (ventral) fin had partially regenerated when the 

 fish was killed. In the toadfish (Opsanus tau) the pectoral fins re- 

 generated only very slowlj^. In none of these experiments is it stated 

 that a fin was cut away closely at its base. There seems to be no 

 evidence that Giinther's original statement is incorrect. It was 

 shown that in ordinary temperatures the beginning of regeneration 

 is almost immediate where it does occur; hence it is perfectly safe to 

 assume that in the removal of the adipose dorsal in the salmon no 

 regeneration occurs, since no beginning of a new growth is evident 

 several months after its excision. Nor do these experiments militate 

 against the results of the Loring experiment of entire amputation of 

 the ventrals, cited above. It is probable that in very cold water the 

 beginning of regeneration will be much delayed. 



SALMON IN THE TROCADERO, AT PARIS. 



The most unassailable evidence of the age of king salmon adults 

 has been rendered by the aquarium of the Trocadero'', in France. At 

 that institution king salmon from eggs obtained in California have 

 been reared for some twenty-five years, generation after generation. 

 It has been found that four years is the usual age, but that females 

 may mature in three and in some cases not until five years. The males 

 are found to be more precocious, some maturing in their second year. 

 This precocity is noted in nature in the "grilse" of the Sacramento 

 and the "Arctic salmon" of the Alaskan sockeye. The occurrence 

 of abnormally large fishes may be due to the delay of maturity until 

 the fifth year. It was found at the aquarium that fish invariably 

 died soon after completion of spawning. 



o Jordan, Guide to the study of fishes, vol. i, p. 150. 



b Bulletin de la Soci6t6 Nationals d'Acclimatation de France, October, 1905. 



