340 



I N A G U A 



float freely with the waves and current. This accounts for the 

 minute dentition, for plankton feeders have little or no use 

 for teeth. 



Fins in most fish serve as rudders, balancers, brakes, or 

 ailerons. It remained for the sharks to put them to a more 

 remarkable and important purpose. The ventral fins of male 

 sharks are produced into a long rod-like process which possess 

 a hollow groove. The function of these modified fins, or clasp- 

 ers, as they are commonly termed, is to carry the life-creating 

 sperm to the body of the female where the eggs are fertiUzed. 

 Consider what an intelligent provision this is. It is not only a 

 means of insuring proper fertilization of the waiting ova, but 

 IS a distinct economy. There is none of the terrific waste com- 

 mon to so much marine fife, none of the lost milHons of sperm 

 cells cast loose to drift away on the tide, their destiny unful- 

 filled. Nor is there the corresponding loss of eggs because of 

 lack of union with the fertilizing element. This is another rea- 

 son why sharks thrive undiminished while other fishes have 

 their seasons of scarcity and why they have continued where 

 more complex types have gone out of existence. 



Life and arithmetic are associated in exact proportions. The 

 number of young that the shark produces, just as in other fishes, 

 is in precise ratio to their chances of survival. In this respect 

 the sharks maintain an almost human ratio. Some of the vi- 

 viparous species are known to produce only two or three 

 young; a dozen is usually considered a maximum family. Con- 

 trast these figures with those of a cod which must extrude up 

 to 9,000,000 eggs to keep its race alive. While the fertilization 

 of shark ova is accomplished in most of the species in much 

 the manner described, they are still somewhat versatile in their 

 methods of reproduction. A great many forms bring forth their 

 young alive— a surprising action in such a primitive animal— 

 and an equal number lay eggs. Here again we see the laws of 



