WEISMANN'S THEORY OF THE GERMPLASM 47 



There must, then, be contained in the cells of the 

 bud the germinal rudiments of the whole animal ; 

 this conclusion is more necessary as the individuals, 

 produced from the buds, in due course bear sexual 

 products. 



Although in many higher animals and plants 

 one sees that cells with the capacity for repro- 

 duction are limited to special areas, still, the 

 capacity for regeneration often is very great. In a 

 wonderful fashion animals will reproduce lost parts, 

 sometimes of most complicated structure ; just as 

 a crystal, from which a corner has been chipped, 

 will perfect itself again when brought into a solu- 

 tion of its own salt. A Hydra, from which the 

 oral disc and tentacles have been cut off, a Nais 

 deprived of its head or of its tail, a snail of which 

 a tentacle with its terminal eye has been amputated, 

 will reproduce the lost parts, sometimes in a very 

 short time. The cells lying at the wounded spot 

 begin to bud, producing a layer or lump, the cells 

 of which resemble embryonic cells. From this 

 embryonic mass of cells the lost organs and tissues 

 arise in Hydra, the oral disc with its tentacles ; 

 in Nais, the anterior end with its sense-organs and 

 special groups of muscles ; in the snail, the tentacle 

 with its compound eye built up of elements so 

 different as retinal-rods, pigment-cells, nerve-cells, 

 lens, and so forth. 



Even among vertebrates, in which the capacity 

 for regeneration is the least, as in the restoration of 

 the wounded parts small defects occur, lizards 

 can reproduce a lost tail, tritons an amputated 



