LARVAL FISHES : THEIR METAMORPHOSES. 129 



lungs, whilst the internal gill supports become 

 modified to serve as supports for the tongue. In 

 the higher vertebrate, for many reasons into which 

 we cannot enter now, the gill-breathing stage is 

 entirely suppressed, but even in man himself the 

 gill-slits and arches still appear during the early 

 stages of his development. Out of these last 

 indeed, as in the frog, the supports for the tongue 

 are made. The nature of the transformations 

 and modifications which give rise in turn to 

 continuous fin-folds and fins, and the gradual 

 evolution of the latter into walking limbs, for 

 the support and carriage of the body on land, we 

 have already sketched in an earlier chapter. 



So much for the typical and primitive larval 

 stages. Let us now turn to some of the more in- 

 teresting of the stages through which some larval 

 fish pass, on their way to the adult condition. 

 Perhaps one of the most remarkable of these is 

 that of the young of our common fresh-water 

 eel. 



Until quite recently the early history the 

 babyhood, so to speak of the common eel was 

 enshrouded in mystery, and was regarded as a 

 zoological puzzle which would reveal itself in 

 due time. Some, anxious to hasten this longed 

 for time, allowed their imagination to carry 

 them beyond the sure grounds of fact into the 

 domains of romance ; or, at any rate, setting aside 

 all caution, they gave full vent to fancy, with the 

 result that fact and fiction were woven together 

 with dire results to truth. The outcome of this 

 unholy combination (in science) was a theory to 

 the effect that eels were developed from horse- 

 I 



