302 SEA-SIDE STUDIES. 



where they repeat the original process of subdivision, and 

 produce offspring as they 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 Partheno- 

 genesis. In j)roportion 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 ar-e in- 

 capable of reproduction. " The reproduction of parts of 

 higher animals has also been found to depend on pre-existing 

 cells retained as such. T\Ir 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 indifferently, 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 generation 

 is ever completed ? Wliy does not the Polype conthme bud- 

 ding off fresh Polypes for ever ; why does not the Aphis-larva 

 continue producing broods of larvae ; why does not the plant 

 persist in sending forth leaves and buds ; why do we always 

 see a sudden change — a leap, as it were, into higher life — 

 completing the cycle by the Polype producing a Medusa, the 

 larval Apliis producing an Aphis, the plant producing a 

 flower ? To this question Owen has prepared an answer. 

 The origmal cell, in its frequent subdivision, gradually loses 



