486 



NATURE 



\Oct. lo, 1872 



ward ; but when placed witliin five or six feet of the hen mother, 

 they, in answer to her call, Ijecame much more lively, began to 

 make little forward journeys, and soon followed her by sound 

 alune, though of course blindly. Another experiment consisted 

 in rendering chickens deaf for a time by sealing their ears with 

 several folds of gum paper before they had escaped from tlie 

 shell. These, on having their ears opened when two or three 

 days old, and being placed Avithin call of the mother concealed 

 in a box or on the other side of a door, after turning round a few 

 times ran straight to the spot whence came the first sound they 

 had ever lieard. Clearly, of these chickens it cannot be said 

 that sounds were to them at first but meaningless sensations. 



One or two observations favourable to the opinion that animals 

 have an instinctive knowledge of their enemies may be taken for 

 what tliey are worth. When twelve days old one of my little 

 //•.i/4'/j' running about beside me, gave the peculiar chirp where- 

 by tiiey announce the approacli of danger. On looking up, a 

 sparrow-hawk was seen hoveruig at a great hciglit over head. 

 Again, a young hawk was made to fly over a hen with her first 

 brood of chickens, then about a week old. In the twinkling of 

 an eye most of the chickens were hid among grass and bushes. 

 And scarcely had the hawk touched the ground, about twelve 

 yards from where the lien liad been sitting, when she fell upon it, 

 and would soon have killed it outright. A young turkey gave 

 even more striking evidence. When ten days old it heard the 

 voice of the hawk for the first time, and just beside it. Like an 

 arrow from the bow it darted off in the opposite direction, and 

 crouched in a corner, remained for ten minutes motionless and 

 dumb with fear. Out of a vast number of experiments with 

 cliickens and bees, though the results were not uniform, yet in 

 the great majority of instances the chickens gave evidence of in- 

 stinctive fear of these sting-bearing insects. 



But to return to examples of instinctive skill and know- 

 ledge, concerning which I think no doubt can remain, a 

 very useful instinct may be observed in the early atten- 

 tion that chickens pay to their toilet. As soon as they 

 can hold up their heads, when only from four to five hours 

 old, they attempt dressing at tlieir wings, that, too, when they 

 have been denied the use of their eyes. Another incontestable case 

 of instinct may be seen in the art of scraping in search of food. 

 Without any opportunities of imitation, chickens begin to scrape 

 when from two to six days old. Most frequently the circum- 

 stances are suggestive ; at other times, however, the first attempt, 

 which generally consists of a sort of nervous dance, was made on 

 a smooth table. The unacquired dexterity shown in tlie capture 

 of insects is very remarkable. .'V duckling one day old, on being 

 placed in the open air for the first time, almost immediately 

 sna]iped at, and caught, a fly on the wing. Still more interest- 

 ing is the instructive art of catching flies peculiar lo the turkey. 

 When not a day and a half old I observed a young turkey, whicli 

 I had adopted while yet in the shell, pointing its beak slowly 

 and deliberately at flies and other small insects without actually 

 pecking at them. In doing this its head could be seen to shake 

 like a hand that is attempted to be held steady by a visible eflbrt. 

 This I recorded when I did not understand its meaning. For it 

 was nok until afterwards that I observe 1 a turkey, when it sees a fly 

 settled on any object, steals on the unwary insect with slow and 

 measured step, and, when sufficiently near, advances its head 

 very slowly and steadily until within reach of its prey, which is 

 then seized by a sudden dart. In still furtlter confirmation of 

 the opinion that such wonderful examples of dexterity and cun- 

 ning are instinctive and not acquired, may be adduced the signi- 

 ficant fact that the individuals of each species have little capacity 

 to leani anything not found in the habits of tlieir progenitors. A 

 chicken was made, from the first and for several months, the 

 sole companion of a young turkey. Yet it never showed the 

 slightest tendency to adopt the admirable art of catching flies 

 that it saw practised before its eyes every hour of the day. 



The only theory in explanation of the phenomena of instinct that 

 has an air of science about it, is tlie doctrine of Inherited Associa- 

 tion. Instinct in the present generation of animals is the pro- 

 duct of the accumulated experiences of past generations. Great 

 difficulty, however, is felt by many in conceiving liow anything 

 so impalpable as fear at the sight of a bee should be trans- 

 mitted from parent to offspring. It should be remembered, how- 

 ever, that the permanence of such associations in the history of 

 an individual life depends on the corresponding impress given to 

 the nervous organisation. We cannot, strictly speaking, expe- 

 rience any individual act of consciousness twice over ; but as, by 

 pulling the bell-cord to-day we can, in the language of ordinary 

 discourse, produce the same sound we heard yesterday, S3, 



while the established connections among the nerves and nerve- 

 centres hold, we are cnaiiled to live our experiences over again. 

 Now, why should not those modifications of brain- matter, that, 

 enduring from hour to hour and from day to day, render acqui- 

 sition possible, be, like a ny other physical peculiarity, transmitted 

 from parent to offsp ring? That they are so transmitted is all 

 but proved by the facts of instinct, while these, in their turn, 

 receive their only rational explanation in this theory of Inherited 

 Association. 



ON THE TREE-FERNS OF THE COAL MEA- 

 SURES, AND THEIR AFFINITIES WITH 

 EXISTING FORMS* 



T INDLEV and Ilutton describe two species of tree-ferns from 

 tlie Coal Measures, both from the Bath Coal-field. I have 

 been able to add eiglit species hitherto undescribed, chiefly through 

 the assistance of Mr.J. M'Murtrie, of Radstock. These belong 

 to three groups, wliicli are remarkably distinguished by peculi- 

 arities in the structure of the stems. Two of the groups belong 

 to living forms, while the third is extinct, being confined to 

 Paleozoic formations. CaiUopteris and Tubicanlis belong to the 

 same type as the living ferns which possess stems, including 

 under this term the humble stems (falsely called rhizomes) of 

 many of our British species, as well as the arborescent ferns of 

 warmer regions ; and excluding the rhizomatous forms like 

 Ptcris, Polypodittm, and Ilymenophylluin. In all these stems we 

 have a central medulla, surrounded by a continuous vascular 

 cylinder penetrated regularly by meshes, from the margins of 

 which the vascular bundle or bundles to the fronds are given off, 

 and through which the parenchyma of the medulla is continuous 

 with that of the stipes. In most tree-ferns the medullary axis is 

 larger, and the bases of the stipes decay down to the circum- 

 ference of the stem, but in Osinnnda the persistent bases of the 

 stipes permanently clotlie the small vascular cylinder which en- 

 closes a slender pith. To this latter form belongs the stipe with 

 a dumbell-shaped vascular bundle, separate specimens of which I 

 have obtaineil from tlie Coal Measures. Tlicse have been de- 

 scribed both on the Continent and in this country, under the 

 name of Zygoplcris, but they belong to Cotta's genus Tuhkatilis ; 

 and they are \ery closely allied to a group of fern stems which I 

 have already placed together under the name of Chdepteris. 

 The stem structure of the common tree-fern is represented by the 

 genus Caulopliris, of which I have six species of carboniferous 

 age. 



The third and extinct group is represented by Corda's genus 

 Slcmmaioptcris, only now known to be British, and hy Psaronins, 

 whicli is, however, not a separate generic form, but only the 

 internal structure of the stems of which Corda's genus is the 

 external aspect. Tlie chief characters of Psiuwiitis have been 

 drawn from the structure of the aerial roots which invest the 

 stem, from which, indeed, the generic designation was derived ; 

 while the structure of the stem itself has been overlooked. But 

 this is really of the first importance, as will appear from the fol- 

 lowing description which I have been able to make from a finely 

 preserved specimen of an undescribed species in the British 

 Museum, and from the figures of Cotta and Corda. The cir- 

 cumference of the stem was composed of a continuous envelope 

 of indurated tissue ; \\'ithin this tliere were perpendicular tracts 

 of vascular tissue never penetrated by any mesh. Between these 

 tracts the leaves were given off in perpendicular series, the large 

 single leaf bundles coming right out from the central parenchyma, 

 where they existed as well-formed bundles, filling up more or 

 less completely the medullary cavit)'. In one form (Zippca] llie 

 leaves are opposite, and the great proportion of the circumference 

 of the stem is made up of the persistent and common vascular 

 tissue ; in others (species of Psaronins) the permanent elements 

 of the stem consists of three, four, six or more perpendicular 

 tracts. 



Tlie first two groups are analogous in the arrangement of the 

 part! of their stems to that which exists in the first year's growth 

 of a dicotyledon. In both there is a parenchymatous medulla 

 surrounded by a continuous vascular cylinder, which is perfo- 

 rated in regular manner by meshes for the passage out of the 

 vascular elements of the appendages. The stems of the third 

 group have a structure analogous to that which is found in the 

 stems of monocotyledons, for in both we have the vascular 



* Paper re.id before the Rritish Association at Brighton in Section C, 

 Aug. 19, by W. Carruthcrs, F.R.S. 



