234 



SCIENCE-GOSSIP. 



INSTINCT. 



By R. Dickson-Bryson, B.A., F.P.S., F.R.As.S. 



(Continued from page zoy.) 



Carnivorous Plants. 

 TV /TANY people, although little interested in the 

 details of attainable science, are curious 

 enough to pry into the recesses of the obscure, 

 where certain knowledge is impossible. This is the 

 region of conjecture and dispute. Still, between 

 the known and the unknown there is a line of 

 demarcation on the frontiers of which we may 

 safely indulge our incursive curiosity ; to pass 

 that boundary is forbidden, and at present im- 

 possible. We must have a care, therefore, not to 

 be dogmatic, and ever keep in mind that here we 

 are in the fairyland of speculation, engaged in a 

 pursuit perhaps not wholly without charm, and 

 certainly not altogether lacking utility. This 

 pursuit is of intense interest when the object is to 

 trace out the unity of nature, and that in a pre- 

 eminent sense when the unity is that between the 

 plant and animal kingdoms. 



Most of us have very hazy notions of what plants 

 and animals really are ; and few, perhaps, would 

 be willing to concede that the difference is not 

 absolute, but merely one of degree. To define the 

 limits, however, and say where the one ends and 

 the other begins, has always been a difficulty, and 

 even now is a conundrum in biology. Probably a 

 satisfactory definition will never be found, since 

 the tendency of all modern scientific results is to 

 obliberate all such strongly marked distinctions 

 and systems of classification. 



Organisms exist which at one period of their life- 

 history are plants, and at another animals, while 

 the microscope has revealed others which com- 

 bine in their minute structures plant and animal 

 properties. Of these may be" instanced the Epistylis 

 grandis, Charchesium polypnium and the interesting 

 Zoothamnium arbuscula. Plant-animal may sound a 

 little paradoxical, but the proverbial fact is some- 

 times stranger than fiction ; a remark that is true 

 in the case of these tiny creatures. They bridge 

 the chasm between the two kingdoms. In the 

 Epistylis grandis, the trunk and branches are 

 perfectly rigid, while the bell-like flowers are 

 all active with the phenomena of animal life. 

 The Epistylis is aquatic, and delights in still pools. 

 It procures its food by setting up a whirling 

 motion in the water with its fringes, thus 

 diverting floating material into the vortex, where 

 it is seized. Each flower is an independent indi- 

 vidual, and selects its own food. In due time the 

 flower leaves the parent stem, and settles down to 

 found a family ot its own. It first develops a 



stalk, and fixes it to a steady object, then its 

 activity ceases — it appears to sleep. During this 

 period it contracts. This process continues until 

 it has produced its double, a companion soon to 

 be its equal, that will assist in founding a colony 

 similar to the one from which they both migrated. 

 In the composition of these organisms it may be 

 admitted that there is more of the animal than the 

 plant. 



A broad distinction between the two kingdoms, 

 and one sufficient for all practical purposes, may 

 be found in the nature of their food. The plant, as 

 a rule, derives its food from simple substances, 

 such as C0 2 , NH 3 and H 2 0, and has alone the 

 power of forming the material of animal struc- 

 ture, viz., proteine. This the animal cannot make 

 itself, and it becomes one of the cardinal distinctions 

 between the two kingdoms. The animal, on the 

 other hand, must have its food previously prepared 

 and elaborated. A more accurate distinction is 

 that plants convert actual energy into potential 

 energy, while the animal reverses the process, and 

 converts the potential into active energy. Old- 

 fashioned distinctions, it is clear, must be aban- 

 doned. The animal merges into the plant and the 

 plant into the animal, and each shares the properties 

 of the other. We cannot longer regard them as 

 absolutely distinct. The evolution hypothesis 

 implies a bifurcation in the original process of 

 germ development, and previous to that primeval 

 division the germ cells were similar in all respects. 

 This is probably the correct theory. Evidence 

 of its truth may be found in the nature of the 

 carnivorous plants. These remarkable plants lie on 

 the frontiers of the two kingdoms. They are 

 flesh-eating, or, more, properly, flesh-absorbing 

 plants. There is neither mastication nor deglu- 

 tition, yet the digestive process is as complete as 

 in that of the animal. Those who have observed 

 that phenomenon and the operations leading up 

 thereto, cannot have failed to note the marked 

 evidences of instinct. The pitcher-plants (Nepen- 

 thes), sun-dews (Droseia), and Venus fly-traps 

 (Dionaea) act as snares, retaining insects which 

 alight on them. It has been conclusively shown 

 that these insects contribute to the nutrition of the 

 plant ; but what chiefly concerns us and our 

 purpose are those curious movements of the leaf 

 analogous to acts of prehension in animals. 



The pitcher-plants (Nepentlics) of the East 

 Indies have their leaves terminated in a pitcher- 

 like glandular structure which secretes a digestive 



