A STUDY OF LOWER LIFE. 55 



be discerned. The polypes are thus literally sensitive, with- 

 out possessing any appreciable or visible apparatus for exer- 

 cising that sense. The hydra is, however, by no means 

 alone in this respect. The sea-anemones (Fig. 3), animals 

 nearly related to the hydra, are equally, if not more sensi- 

 tive than the latter; since the anemones may be seen to 



FIG. 3. Sea-anemones : A, expanded ; B, contracted. 



withdraw their tentacles and to contract their bodies if the 

 light falling upon them be suddenly intercepted, as by the 

 shadow of a passing cloud. Yet the anemones, like hydrae, 

 want a definite nervous system. But certain plants may 

 also not only exhibit symptoms of irritation or sensitiveness 

 when touched, but may act upon their sensations, features 

 well exemplified by the drooping leaflets and leaf-stalk of the 

 sensitive plant ; by the closure of the leaf of the Venus' fly- 

 trap ; and by definite movements of contraction observed in 

 other plants, resulting from alterations in temperature. In 

 plants, it is almost needless to remark, no nervous system 

 has been demonstrated to exist ; and no botanist has even 

 suggested the possibility of the existence of nervous tissues 

 within the limits of the vegetable creation. Yet, tested by 

 the acts of their lives, one might truly say to such plants, 

 with Shakespeare, 



" Sense you have, 

 Else could you not have motion : " 



and judging from the sensitiveness of the plants just 

 mentioned, the conclusion appears inevitable, that plants 



