5i8 



SCIENTIFIC NEWS. 



[June I, if 



That the carbonic acid exhaled by the mites is ser- 

 viceable to the plant Lundstrom infers from the circum- 

 stance that those parts of the leaves which are tenanted 

 by mites remain green longest in autumn. 



In conclusion, Lundstrom gives a conspectus of 

 symbiotic formations. Under this name he includes all 

 structures in plants occasioned or established by foreign 

 organisms, and in which such organisms undergo an 

 essential part of their development. According as the 

 symbiosis (association) is antagonistic or mutual, the 

 formations produced are called cecidia or domatia. 



It will be apparent from Dr. Lundstrom's researches 

 that the mutual relations of plants and animals have not 

 all been thoroughly explored. Further investigation in 

 this direction is needed, and will doubtless reward the 

 patient observer with discoveries concerning the economy 

 both of animals and plants. 



THOUGHTS ON INSTINCT.— II. 



{Concluded from p. 495.) 



IN thus acting there can be nothing unphilosophical. 

 But we are bound to find out, if possible, what is this 

 unknown power. We must ascribe to it no more than 

 is plainly needful. We must note, too, that the instinctive 

 shrinks up and draws back on close examination. In 

 other words, many actions which were once called 

 instinctive are now found traceable to instruction, imita- 

 tion, or to knowledge otherwise acquired, or, finally, to 

 the teachings of reason. 



It has also been shown that much of what, in the 

 actions of the lower animals, seems to us inexplicable is 

 due to the greater acuteness of their senses, or, in case of 

 insects, to their possession of senses, other, or even more, 

 ■than our own. That many vertebrate animals far surpass 

 us in the delicacy of tiieir sight, smell, or hearing is no 

 longer a matter under discussion. As for insects, a 

 variety of points connected with their structure, and, 

 ■ still more, a number of observations upon their conduct, 

 almost compel us to admit that they possess inlets of 

 knowledge of whose nature we can form no direct con- 

 ception. 



Within the domain of sight there are regions closed 

 - against us. The retina of the human eye is sensitive to 

 a portion only of the sun's rays. If we throw the solar 

 spectrum upon a screen, we see the seven so-called 

 spectral colours in their usual order. But above and 

 below these bands of colour there are radiations whose 

 presence we can show by appropriate physical and 

 chemical means, but which, to our organ of sight, are 

 simply darkness, If the eyes of any creature — or its 

 entire frame — be sensitive to the whole or to a part of 

 these " dark rays," as we call them, such creature will be 

 able to see where we find total darkness, and to see 

 illuminated objects as we do not see them. If, then, 

 certain animals possess more acute and perhaps more 

 numerous senses than do we, they are in a condition to 

 acquire by direct perception knowledge which we can 

 gain only by trains of inductive reasoning, and by the use 

 of instruments of precision. Very probably most of 

 those instances of alleged instinct which are not 

 resolvable into hereditary habit depend on a simple 

 following of the guidance of senses more acute than our 

 own. We must never forget that to all animals, and 

 jiot less to uncivihsed man, every strange object is 



unpleasant, and is either attacked or fled from according 

 to circumstances. 



Trappers in the Rocky Mountains declare that even 

 the redoubtable grizzly, if the scent of a man is 

 brought down to him on the wind, becomes uneasy, 

 and quickly gets out of reach of the unknown 

 impression. When a bun, wet with prussic acid, 

 was thrown to a superfluous bear in the Jardin des 

 Plantes, we were treated to much high-flown declama- 

 tion because the animal, instead of at once devouring 

 the bun, first washed it in a little channel of water 

 flowing through his enclosure. Now this action was 

 plainly due, not to any instinctive knowledge of the 

 properties of prussic acid, but simply to the bears' 

 distrust of an unusual smell. 



That acquired habits may become hereditary, re- 

 appearing without any special instruction or example in 

 succeeding generations, is shown by such familiar 

 instances as the pointer, the retriever, and and the sheep- 

 dog. Bird's-nests have been vociferously appealed to as 

 instances of a mysterious instinct. Say the rhetori- 

 cians : — " It cannot be imitation, for, though you hatch a 

 crow under a hen and never let it see any of the works 

 of its kind, the nest it makes will be the same, to the 

 laying of a stick, with all the other nests of the same 

 species. It cannot be reason; for were animals endowed 

 with it to as great a degree as man (note the sophism !), 

 their buildings would be as different as ours, according 

 to the different conveniences they would propose to them- 

 selves." 



This sounds, to the non-naturalist, very plausible. But 

 we are perfectly warranted in referring the general 

 similarity of the nests of any one species to hereditary 

 habit. The second part of Addison's argument is sophis- 

 tical : — " It cannot be reason ; for were animals endowed 

 with it to as great an extent as man" etc. This is what 

 no one contends; observers of Nature maintain that the. 

 lower animals are endowed with it to a much less degree 

 than is man, such a less degree being fully sufficient. 



Further, as Mr. A. R. Wallace has ably shown, the 

 habitations of birds are modified according to circum- 

 stances. We even learn that the European sparrow, 

 introduced into North America, builds itself there a 

 winter-nest for shelter during the inclement season, quite 

 different from its breeding-nest. On the other hand, 

 man, in the construction of his dwellings and in many 

 other matters, often evinces an adherence to hereditary 

 customs, little in accordance with reason. 



The region where in addition to actions evidently 

 rational we meet with others for which reason does not 

 at first sight seem to account is the insect world. As we 

 find so much difficulty in comparing the senses of inver- 

 tebrate animals with our own, we are still less able to 

 fathom their mental nature. To pronounce their actions 

 "instinctive" is, therefore, an indirect and not over 

 candid way of confessing, and at the same time shuffling, 

 over our own ignorance. Far better to make a bold 

 avowal of our limited knowledge, and strive patiently 

 and earnestly for its extension. The instinctarian of the 

 old school does neither. 



Perhaps it will be found that the finishing stroke to the 

 doctrine of instinct, viewed as a mysterious substitute for 

 reason, has been dealt by the elder Darwin, and has 

 again been brought under notice by Mr. Samuel Butler. 

 These writers pronounce instinct to be simply " inherited 

 memory." Each animal is simply a continuation, or, as 

 Dr. Darwin expressed it, a " prolongation," of the life of 



