INFANCY OF CRABS AND CATERPILLARS 237 



of spirits, in the form of gambols. No record of such 

 vitality has been recorded of young reptiles, or of the 

 frog tribe, but I have seen young fishes in the Norfolk 

 Broads absolutely revelling in the summer sun ; turning 

 and twisting till their silvery bodies glistened, now shooting 

 along the surface, and now diving into the cool depths 

 as if to avoid some imaginary foe. But with the In- 

 vertebrates there is no such demonstrativeness : on the 

 contrary, some of these reveal an almost criminal de- 

 pravity ; while for the most part they give no sign of the 

 consciousness of life, no indication that they are either 

 glad to be ahve, or find life a bore ! It is then for the 

 strange contrasts of shape and the curious history of 

 these early phases that we must study them. Among 

 the lowest groups of all there is no childhood, no period 

 of infancy. 



In these pages it will be impossible to do more than 

 select a few of the more striking illustrations of the 

 infantile period among the invertebrates, for the number 

 of species they embrace represents a colossal total. The 

 insects alone far outnumber all the land animals of the 

 world, while the vertebrates compared therewith form 

 but an insignificant band. 



But, if only by way of affording a contrast with what 

 has gone before, it is worth while to take a survey of some 

 of the more striking cases of infancy among these lowly 

 creatures. And no better introduction to this theme 

 could be found than that furiiished by some of the aquatic 

 types — as for example the Crustacea. 



If a fine muslin net be towed at the surface of the sea 

 on a calm day, and the contents turned out into a jar of 

 sea-water, it will be found to have captured, among other 

 things, clouds of animated specks, which dance in the 



