THE INFANCY OF FISHES 227 



One little stump projecting from the back of its head 

 foreshadows the fin-rays that are soon to sprout, and a 

 few blotches of black pigment give emphasis to the general 

 transparency of its body. In a few days more two fin- 

 rays have made their appearance on the back, and a pair 

 on each side depend from the belly, these last answer the 

 hind-limbs. The fore-limbs or breast fins have now ap- 

 peared, and the free edge of the right fin may be seen as 

 a broad semicircle across the body. Now compare these 

 with the still later stage. AU the fins which it will ever 

 have are now present, but they have still further changes 

 of shape to undergo. 



In the oldest of these larval stages, it will be noticed, 

 the foremost fin is composed of a number of hook- 

 shaped rods united at the base by a thin sheet of 

 transparent skin, which is continued backwards to em- 

 brace the second back fin. The breast fin is now 

 large, but the most striking change of all has occurred 

 in the form of the fins which answer to the hind-limbs. 

 These, it will be seen, form two enormously elon- 

 gated streamers, much longer than the whole body. We 

 can only surmise that they serve as organs of touch and 

 are highly sensitive. But why are such intelligences 

 needed at this particular stage of life ? And what, 

 it may be asked, is the meaning of the striking difference 

 in the form of the tail as compared with the younger 

 stages ? To the first question Science has, as yet, no 

 answer ; to the second we must return presently. 



Remarkable as are the differences displayed between 

 these three stages, they become stiU more accentuated 

 when we come to compare them with that of the adult. 

 The young fish has a cylindrical body, and is apparently 

 free-swimming. It is certainly comely in appearance. 



