FINS : THEIR USES. 65 



structures. In other words, the facts disclosed in. 

 this study of transformations lead us to hope that 

 we may get some insight into the origins of fins. 

 Scientific experts are generally agreed that 

 the earliest fishes possessed no true fins. Loco- 

 motion was performed by means of vigorous side 

 to side strokes of the tail, aided by undulatory 

 movements of the whole and probably much 

 elongated and cylindrical body. In other words 

 progression was eel-like. This mode of progres- 

 sion was soon followed by the appearance of the 

 first fin. An attempt to account for the origin 

 of this was the subject of an ingenious experi- 

 ment adopted by Mr J. T. Cunningham. He 

 took an ordinary penholder and cuated it evenly 

 and thinly with wax. Then holding it by one 

 end, he moved it rapidly from side to side in a 

 basin of hot water. The pen being held in a 

 horizontal position, soon a vertical ridge made 

 its appearance above and below, and this gradu- 

 ally increased in size till, in about five minutes, 

 there was an upper and under ridge half-an- 

 inch in height, corresponding, as he points out, to 

 the median fins — the dorsal and anal and caudal 

 or tail-fins described on p. 12. The presence 

 of these median fins was a distinct gain to the 

 fish. A still further advance took place, when 

 the lower or undermost vertical fin, near the 

 middle of the abdomen, divided into two and ran 

 forwards on either side of the abdomen as a pair 

 of thin membranous folds terminating at the 

 head (fig. 7, A.). The fish was now really well- 

 balanced, but improvement was yet possible. 

 Numerous rods or bars of cartilage now appeared 

 E 



