252 DESIGN IN NATURE 



vacuoles, spaces, or cavities of about ttoVtt of an inch in diameter, which contract with regular rhythm at intervals 

 of from thirty-eight to forty-one seconds, quickly contracting and then more slowly dilating again." 



Sir James Paget adds : " The observations of Cohn,^ pubhshed about a year later than those of Mr. Busk, but 

 independent of them, discovered similar phenomena in Gonium pectorale and in Chlamydomonas , the vacuoles, like 

 water- vesicles, contracting regularly at intervals of forty to forty-five seconds. The contractions and the dilata- 

 tions occupy equal periods, as do those of our own heart ventricles ; and in Gonium he has fovmd this singular fact, 

 that when, as commonly happens, two vacuoles exist in one cell, their rhythms are alike and exactly alternate, 

 each contracting once in about forty seconds, and the contraction of each occurring at exactly mid-distance between 

 two successive contractions of the other. Here, then, we have examples of perfect and even compound rhythmic 

 contractions in vegetable organisms, in which we can have no suspicion of muscular, structure, or nervous, or of 

 stimulus (in any reasonable sense of the term), or, in short, of any of those things which we are prone to regard as 

 the mainsprings of rhythmic action in the heart." ^ 



The movements in the insectivorous plants are more or less rhythmic and definitely co-ordinated. They are 

 also movements to a given end, and purpose-like, namely, the securing of living flies and small insects as food. 

 Examples of these movements are to be seen in Venus's fly-trap {Dionma muscipula) and the sun-dew (Drosera 

 rotundifolia). Arrangements for catching live insects are also met with in the pitcher plants. 



In Venus's fly-trap the outer portion of the leaf bifurcates, is orate, slightly saucer-shaped, and provided with 

 serrated edges and six exceedingly sensitive hairs, three on each half of the leaf, which project from the surface, 

 and are consequently in the way of anything moving on the leaf. When any small insect (fly, beetle, &c.) settles 

 and crawls on the leaf it inevitably comes in contact with the sensitive hairs, and the plant, being informed of the 

 presence of the insect, slowly but surely imprisons, crushes, and destroys it. Nor does the marvel stop here. No 

 sooner is the insect fairly within the grasp of the leaf than a secretion, akin to gastric juice, is poured forth from 

 glands on its surface which enables the plant hterally to devour and assimilate the insect. The leaf remains closed 

 until the process of assimilation is completed, when it gradually opens to receive a new victim. Nor is this all. 

 If the plant be tricked by dropping a small piece of cork or some non-edible particle on a leaf, it closes the leaf, but 

 soon again re-opens it ; no digestive fluid whatever being exuded. The plant can therefore distinguish between 

 what is edible and what is non-edible. This impUes a low form of cognition or its equivalent. The opening and 

 closing of the leaf and the production of a digestive fluid cannot be regarded as, in any sense, haphazard. 



When we consider that the spontaneous, definite, co-ordinated movements of Venus's fly-trap are performed 

 m the absence of bones, muscles, nerves, and all those structures which are usually associated with the production 

 of purpose-hke movements in animals, they are, to say the least, very remarkable. They, in a sense, widen the 

 horizon of organic movement indefinitely. They show that the potentiahties of Uving matter are practically un- 

 hmited. Motion, purpose-hke motion, can no longer be regarded as the prerogative of animals. That the move- 

 ments of the fly-trap are not due to irritation in the ordinary sense is proved by this, that they will close on living, 

 edible, and dead, non-edible particles ahke. There is, however, this astonishing difference : the leaves remain closed 

 on edible particles until they are digested and assimilated, whereas they open and extrude non-edible particles. 



If the food of the plant acted as an irritant, the plant would naturally get rid of it with all possible haste. This, 

 as explained, it never does. The substances which it will not tolerate are the non-edible ones. 



RHYTHMS AND REFLEXES IN PLANTS AND ANIMALS: THEIR 



NATURE AND USES 

 Rhythms in plants and animals may be defined as involuntary movements recurring at stated intervals • the 

 movements bemg repetitions of each other, and the intervals varying according to circumstances. They are funda- 

 mental inherent, and intimately associated with hfe in its several phases : indeed hfe without rhythms would be 

 impossible, as they are, to a large extent, the means by which nutrient materials are added to hving bodies and the 

 detritus or waste products carried off. They, in conjunction with certain reflex acts, are responsible for aUmentation, 

 respiration, circulation, reproduction, secretion, excretion, and various important functions, the due performance 

 of which IS necessary not only to the well-being but also to the existence of the individual. The rhythm, make their 

 appearance at the very threshold of life in rudimentary plants and animals as contractile vesicles, and they 



Zr TU^"Z"f^r7 "^ "" -'"f '" ?.' ''''''' °' differentiation attained by plants and animals respec- 

 tively. Ihis IS especially the case m ammals. Rhythms, in the mdest sense, are accountable for most if not all 



•28, 1857 



L,oo„,a,> Lectuio, On the Ca,>so of the El.ythnuc Motion of the Heart," l,y Su- James Paget, Bart., F.R.S. Proc. Roy. Soc, May 



