12 



NATURE 



\_Nov. 2, 1 8; I 



generalisation as to the probable gold-bearing nature of 

 the Australian quartz-country, and as to the probable 

 aspect of the interior of Africa, are probably familiar to 

 most people. But in later years what has especially 

 brought hiS name into prominence is the chivalrous devo- 

 tion with which he has maintained one might almost say 

 the national belief in the welfare of Dr. Livingstone. Yet 

 this is only a sample, though one which has come more 

 publicly before us, of the tenacious friendship and active 

 benevolence which have always marked him. As Presi- 

 dent of the Geographical Society — a society which is in a 

 sense his own creation — he had frequent opportunities of 

 befriending not only the cause of geography but the per- 

 sonal well-being of travellers, and he never failed to use 

 them. The geographers have good cause to lament the 

 death of their chief. 



Of the man himself, what he was as he lived and moved 

 among us, his loss is too recent to permit us justly to 

 speak. We can only think of him as the stately courteous 

 old gentleman, carrying even- to the last that military 

 bearing which dated from the days of Wcllesley and 

 Moore, kindly and thoughtful in his kindliness — a man 

 whose friendship, once given, even ingratitude and in- 

 justice could not wholly alienate. He was not without 

 some of the littlenesses of humanity, but they were so 

 transparent, and often even so child-like, that we forget 

 them in the recollection of all the goodness of heart and 

 strength of head and nobility of nature which have 

 gladdened us for so long, but which are now only subjects 

 of tender remembrance. 



Arch. Geikie 



HOMOPLASY AND MIMICRY 



ALL students of the remarkable phenomenon of super- 

 ficial resemblances in the animal and vegetable 

 kingdom will be glad that Prof Dyer has published an 

 extension of the paper which he read on this subject at 

 the Edinburgh meeting of the British Associr.tion. It is 

 especially satisfactory that he has aijandoncd the very ob- 

 jectionable terra " pseudomorphic,"and substituted that of 

 " homoplastic," a very much better term, because it simply 

 expresses a fact without committing one to any theory. 

 There are, however, one or two points in his paper of last 

 week, on which I should wish to be allowed to comment. 

 Prof. Dyer holds that the distinction between ''mi- 

 micry" in animals and "homoplasy" in plants, is 

 " sufficiently obvious," the difference assigned being, 

 apparently, that in the one case it takes place between 

 species found in the same locality, ia the other between 

 species unconnected geographically. I doubt, however, 

 whether facts will warrant this distinction. The most re- 

 markable instances of "mimicry " among animals hitherto 

 published arc, undoubtedly, in the case of species inhabit- 

 ing the same area ; but I am inclined to think that, when 

 attention is called to the subject, others will be found 

 between animals not so associated, though these instances 

 would naturally not attract so much observation. And 

 secondly, homoplasy in plants docs frequently occur in 

 species occupying the same area. The statement reported 

 to have been made by Prof. Dyer at Edinburgh that " the 

 resembling plants are hardly ever found with those they 

 resemble," would scarcely be borne out by a careful in- 

 vestigation. The real objection to the terms "mimicry " 

 and " imitation " is that they seem to imply a conscious 

 effort at convergence, which will hardly be conceded in the 

 case of Lepidoptera any more than of Ferns. The sub- 

 stantial dift'erente belweeen the two is that, in the case of 

 animals, the resemblance appears to be protective, while 

 in the case of plants, there is seemingly no such benefit 

 arising from it ; but this is a difference in result and not 

 in the nature of the phenomenon itself. I fail to see that 

 the objections to the use of these terms in the case of 



plants do not equally apply to animals ; we have no 

 reason to suppose that the two sets of phenomena are not 

 produced by similar causes. 



Prof. Dyer states, and no doubt truly, that the external 

 resemblances of plants may frequently be traced to the 

 effect of similar external conditions, and quotes in support 

 Mr. E. R. Lankester's view with regard to animals. But in 

 assuming that this explanation will account for all such 

 phenomena if fully investigated, I think too much is 

 assumed. Cases of homoplasy are referable to two distinct 

 classes — resemblances in general habit, and resemblances 

 of particular organs. The former, as in the case of the 

 homoplasy between a Cactus and a Euphorbia or a 

 S/a/'c/ia, or between a Kleinia and a Cotyleaon, are no 

 doubt due to the operation of similar external conditions 

 of climate and soil But in the second class this explana- 

 tion wholly fails. 



As illustrations of the kind of resemblance I mean, I 

 may refer to the two collections of " mimetic plants" ex- 

 hibited by Mr. W. W. Saunders at the two last soirees of 

 the Linnean Society, a list of which will be found in 

 Nature for May 26, 1870, and May 4, 1871. The ex-' 

 traordinary resemblance in the markings of the leaves in 

 plants thus grouped together, might well deceive the most 

 experienced botanist. To account for this homoplasy on 

 the ground of similar external conditions, is to start a 

 mere hypothesis, without any facts to warrant it. y\ still 

 more curious series of resemblances occurs in the case of 

 fruits than of leaves, so close that it has deceived botan- 

 ists of the experience of the elder Hooker, Bentham, and 

 Kunth into placing species in a genus with v/hich they 

 have no structural affinity whatever. I have in my mind 

 in particular two samaroid fruits, both from the forests of 

 Brazil, so absolutely identical in external facies, that dis- 

 tinction is quite impossible without dissection, and yet 

 belonging to exceedingly remote orders. I will not, how- 

 ever, say more on this point, as it would be impossible to 

 appreciate the closeness of the homoplasy without draw- 

 ings, which 1 hope shortly to be able to publish. The 

 singular part of this resemblance is, that, as far as we 

 know, it is never protective. In our Bee-orchis we have 

 what might well have been assumed prima facie to be a 

 case of protective resemblance, the flower being so 

 fashioned in order to attract bees to assist in its fertilisa- 

 tion. It is remarkable, however, that the Bee-orchis is 

 one of the few plants that appear to be perpetually self- 

 fertilised, never being visited by insects. It is just pos- 

 sible that we have an instance of protective or rather 

 beneficial resemblance of scent in the case of the carrion- 

 like odour of the flowers of Stapclia, which attracts blue- 

 bottle and other flies. 



In a paper read at the recent meeting of the American 

 Association for the Advancement of Science, by Prof. E. 

 D. Cope, I find the following thoughtful remarks : — " In- 

 telligence is a conservative principle, and will always direct 

 effort and use into lines which will be beneficial to its 

 possessor. Thus, we have the source of the fittest, i.e., 

 addition of parts by increase, and location of growth- 

 force directed by the will, the will being under the 

 influence of various kinds of compulsory choice 

 in the lower, and intelligent option among higher 

 animals. Thus intelligent choice may be regarded 

 as the originator of the fittest, while natural selection is 

 the tribunal to which all the results of accelerated growth 

 are submitted. This preserves or destroys them, and 

 determines the new points of departure on which accele- 

 rated growth shall build." 



Biologists generally are, probably, hardly prepared to 

 apply the terms "intelligence' and "will" to the vege- 

 table kingdom ; but the use of the term "vegetable life" 

 seems to me to imply of necessity that there are po.vers 

 at work in the economy of the plant, as of the animal, which 

 it is vain to attempt to reduce to manifestations of the 

 forces which govern the inorganic world. 



.\LERED w. Bennett 



