586 



SCIENCE. 



[N. S. Vol. XXIII. No. 589. 



ment of fishes, dealing especially with the 

 caudal as a ' propulsatorisches Organ.' The 

 use of the tail and the flexion of the body 

 have been generally recognized by writers on 

 the fishes. The experiments performed by 

 Duges were made on sharks twenty years ago 

 hy Paul Mayer and accurately described in 

 ' Die unpaaren Flossen,' * with practically the 

 same results. 



The account of Mr. Duges called to mind 

 certain of my own observations made several 

 years ago, but not published. As these were 

 not entirely in accord with those of the above 

 writer I decided to repeat the studies for the 

 sake of confirming either my own work or 

 that of Mr. Duges. Director Charles H. 

 Townsend, of the New York Aquarium, very 

 kindly granted me space and material. I have 

 to thank also Mr. W. I. DeNyse, of the aqua- 

 rium, who assisted me in many ways and 

 confirmed some of the observations. The ex- 

 periments were chiefly upon Fundulus hetero- 

 clitus, a hardy species in which the fins are 

 of rather large size. 



Space will not permit the recounting here 

 of all the experiments made by removing the 

 fins in all possible combinations, but a few 

 of the results may be stated. When a single 

 pectoral fin was removed the fish tended to 

 turn partly on one side, due probably to the 

 action of the pectoral of the opposite side. 

 This, however, the fish soon learned to regu- 

 late. After the removal of both pectorals the 

 fish when swimming slowly apparently moved 

 as usual, but when forced to turn quickly it 

 was unable to accurately balance or otherwise 

 undergo movements requiring nice adjust- 

 ment. This is much more marked in the 

 short, compressed or rhomboidal type of fish. 

 A scup {Sienotomus chrysops) with both pec- 

 torals removed is very helpless when attempt- 

 ing to undergo certain movements which are 

 ordinarily performed with the greatest ease. 

 A study of the movements of the many species 

 of fishes in the New York Aquarium is en- 

 tirely confirmatory of the view that one func- 

 tion of the pectoral is to balance and accu- 

 rately adjust the fish in swimming. 



*Mitth. z. Zool. Sta., Neapel, VI., 1886. 



Another very evident function of the pec- 

 toral, at least in many species, is locomotion. 

 Fundulus occasionally swims slowly forward 

 with the use of the pectorals alone, or it can 

 reverse the movement and swim backward 

 very slowly, and I have even seen them swim 

 slowly in a circle using only one pectoral. 

 These are not to be considered the most or- 

 dinary movements in Fundulus, but at least 

 they show that the fins are capable of being 

 used for these purposes. In this connection 

 the doctor-fish (Teuthis hepatus) is one of the 

 most interesting. This active fish swims 

 rapidly around the aquarium tank with the 

 body apparently quite rigid and, using the 

 pectorals like a pair of wings, can swim either 

 forward or backward. The tautog (Tautoga 

 onitis) often swims leisurely, using only the 

 pectorals and dorsal. 



Another well-marked function of the pec- 

 torals is their use as a drag or brake in stop- 

 ping. It can be noted in the movements of 

 many fishes in the aquarium that in stopping 

 the pectorals, and often the pelvics also, are 

 thrown out at right angles to the body, thereby 

 increasing very greatly the resistance to the 

 water. Fishes with the pectorals removed 

 would at first frequently run against the side 

 or bottom of the tank, but later they learned 

 to avoid this by a strong movement of the 

 tail. During the course of my experiments 

 on this point I was pleased to find in Dr. H. 

 H. Swinnerton's latest paper'' a statement to 

 the same effect, and in a recent conversation 

 Professor R. S. Lull offered the same sug- 

 gestion. 



With regard to the observation made by 

 Mr. Duges that the pectorals are moved when 

 the fishes are stationary in order ' to produce 

 currents in the water to renew the portions of 

 this which had already yielded their oxygen, 

 to the gills and remained charged with car- 

 bonic anhydride,' I must say that, while at 

 first glance it looks like a probable explana- 

 tion, a little study of various types of fishes 

 will serve to show the fallacy of the statement. 

 In the first place the water is not renewed at 



" ' A Contribution to the Morphology and De- 

 velopment of the Pectoral Skeleton of Teleo- 

 stomes,' Q. J. M. 8., November, 1905. 



