86 ANIMAL METAMORPHOSIS. 



generation, where the parent does not produce an organism like 

 itself, or one which even ultimately develops into a form like 

 itself, but something entirely different, which acts merely as an 

 intermediate or " nurse " form, furnished with the necessary 

 organs to preserve its existence until it is able to mature the 

 reproductive elements, or to produce in its substance a young 

 organism which, after various changes, assumes the form and 

 characteristics of the original parent. 



Strange would our experiences be if the processes of metamor- 

 phosis and alternation of generation were adapted to our terres- 

 trial zoology. A popular writer recently suggested, " It would be 

 as though rats produced mice and mice rats ; in fact, that every 

 two sets of animals combined to maintain each other's species, 

 neglecting their own. To obtain sheep we should have to keep 

 goats ; to breed horses, donkeys. Or supposing we had animals 

 that were never the same thing for four and twenty hours together. 

 The cat that sat down on the hearth-rug would gradually develop 

 a multitude of legs and absorb its own head till it looked like a 

 furry crab. Looking round by-and-bye, we should find it in a 

 snake-like form, delicately fringed with alternate ears and tails. 

 Half-way down the street, the cab-horse would become completely 

 spherical, and round the next corner would become elongated 

 microscopically." And, strange as these suggestions seem, they are 

 not more wonderful than what we find actually occurring in the 

 animal world. Organisms in their infancy swimming about mer- 

 rily, lose their active locomotive powers, and creep about upon the 

 ocean floor, some of them at an intermediate stage of their exist- 

 ence being for a time fixed to the bottom Hke a stony plant. 

 Others, which, when young, possess eyes and locomotive organs, 

 lose them in advanced life, and become simple, sac-like parasites, 

 or, encasing their body in a shell of many valves, are rooted for 

 the remainder of their existence to the rock on which they happen 

 to settle. The same creature which at one time has all the char- 

 acteristics of a fish, at another exists as a four-footed amphibian. 

 Eyeless, footless grubs develop into lively insects sporting in the 

 sunshine ; while others, again, passing their infant days crawling on 

 the bottom of a muddy pond, which they match in colour, take on 

 the glittering colours of the emerald and turquoise, and on gauzy 



