320 SEA-SIDE STUDIES. 



themselves were produced. In proportion, therefore, 

 to the complexity of the animal (that is, in proportion 

 to the amount of cells transformed into tissues), will 

 be its inability to reproduce itself by Parthenogenesis. 

 In proportion to the amount of unchanged cells will be 

 this power of reproduction. The marvels of the Hydra, 

 as recounted by Trembley, are thus explicable ; for the 

 Hydra retains its germ-cells unchanged everywhere, 

 except in the tentacles and the integument, and these 

 are incapable of reproduction. " The reproduction of 

 parts of higher animals has also been found to depend 

 on pre-existing cells retained as such. Mr H. D. S. 

 Goodsir has shown that, in the lobster, so noted for 

 the power of reproducing its claws, the regenerative 

 faculty does not reside at any part of the claw indiffer- 

 ently, but in a special locality at the basal end of the 

 first joint. This joint is almost filled by a mass of 

 nucleated cells surrounded by a fibrous and muscular 

 band." 



But here the reader may ask how the cycle of gen- 

 eration is ever completed? Why does not the Polype 

 continue budding off fresh Polypes for ever ; why does 

 not the Aphis -larva continue producing broods of 

 larvse ; why does not the plant persist in sending 

 forth leaves and buds ; why do we always see a sud- 

 den change — a leap, as it were, into higher life — com- 

 pleting the cycle by the Polype producing a Medusa, 

 the larval Aphis producing an Aphis, the plant pro- 

 ducing a flower ? To this question Owen has prepared 

 an answer. The original cell, in its frequent subdivi- 



