VENUS'S FLY-TRAP. 63 



insects of that kind, though always killed, seem to be 

 too hard shelled to serve as food, and after a short 

 time are rejected." 1 



We may here allude to that phase of the subject 

 which was so successfully investigated and illustrated 

 by Dr. Burdon Sanderson, and which amounted to 

 establishing the identity of the phenomena of mus- 

 cular contraction and contractility in Dioncea. The 

 property of contracting when irritated, which enables 

 the Dioncea to catch insects, was the special phase of 

 the subject to which Dr. Burdon Sanderson directed 

 his attention. In this phenomenon, he says, " we have 

 to do not merely with contractility but with irrato- 

 contractility. The fact that the property requires two 

 words to express it implies that there are two things 

 to express, viz. (1) that contraction takes place, and 

 (2) that it takes place in answer to irritation. As 

 this is the case, not only here, but in all other in- 

 stances of animal or vegetable active motion, we 

 recognise in physiology these two properties as fun- 

 damental — irritability or excitability, and contrac- 

 tility, the former designating the property, possessed 

 by every living structure whatever, of being excited 

 into action (/.<?., of having its stored-up force dis- 

 charged) by some motion or disturbance from out- 

 side ; the latter, that kind of discharge or action which 



1 " Gardener's Monthly," August, r868. 



