496 



NA TURE 



[September 21, 1893 



Mr. Beddard gives tables of the results obtained by Weis- 

 ttiann, Poulion, and others, which show that it is impossit)le to 

 lay down any definite law upon the subject, and that the likes 

 and dislikes of insect-eating animals are purely relative. 



One of the most interesting cases of mimicry is that of the 

 Volucella, a genus of Diptcra, whose larvs live on the larvje of 

 Hymenoptcra, and of which the perfect insect closely resembles 

 some species of humble-bee. Though this fact is unquestioned, 

 yet it has recently given rise to a controversy, which, so far as 

 one who has no claim to be an entomologist can jadge, proves 

 that while there is much that can be explained by mimicry, 

 there is, nevertheless, a danger of its advocates pressing it too 

 far. Volucella bombylavs occurs in two varieties, which prey 

 upon the humble-bees, Bombus mnsconan and B. lapidarins, 

 which they respectively resemble. Mr. Bateson does not ques- 

 tion the behaviour of the Volucella, but stales that neither variety 

 specially represents B. muscoriim, and yet that they deposit 

 their eggs more frequently in their nests than in the nests of 

 other species which they resemble more closely. He also states 

 that in a show-case in the Royal College of Surgeons, to illus- 

 trate mining, two sjiecimens of anothtr species, B. sylvarnni, 

 were placed alongside of the Volucella, which they do resemble, 

 but were labelled B. viuscorum. 



But Mr. Hart explains the parasitism in another way. He 

 states that a rest of B. muscorum is made on the surface, 

 without much attempt at concealment, and that the bee is a 

 peculiarly gentle species, with a very feeble sting ; but that 

 the species which the Volucella mrst resemble are irasc ble, and 

 therefore mote dangerous to intruders. If this be so, it is difficult 

 to see why the Volucella should mimic the bee, which it does 

 not affect, more closely than the one which is generally its 

 victim. I do not presume to express any opinion further than 

 this, that the instances I have cited show that there is much 

 reason for further careful observation by the field nauiralist, 

 and much yet to be discovered by the i">hysiologist and the 

 chemist, as to the composition and nature of animal pigments. 



I had proposed to occupy a consideralile portion of my 

 address with a statement of the present position of the contro- 

 versy on heredity, by far the mo*t difficult and important of all 

 those subjects which at present attract the attention of the bio- 

 logist ; but an attack of illness has compelled me to abandon my 

 purpose. Not that I proposed to venture to express any opinions 

 of my own, for, with such protagonists in the field as Weismann, 

 Wallace, Komanes, and Poulion on the one side, and Herbert 

 Spencer and Hartog on the other, " A'on nostrum inter vos 

 ■tantas componere lites." 



So far as I can understand Weismann's theory, he assumes 

 the separation of germ cells and somatic cells, and that each 

 germ cell contains in its nucleus a number of "ids," each " id " 

 representing the personality of an ancestral member of the 

 species, or of an antecedent species. "The first multicellular 

 organism was probably a cluster of similar cells, but these units 

 soon lost their original homogeneity. As the result of mere 

 relative position, some of the cells were especially fitted to 

 provide for the nutrition of the colony, while others undertook 

 the work of reproduction." The latter, or germ-plasm, he 

 assufties to possess an unlimited power of continuance, and that 

 life is endowed with a fixed duration, not because it is contrary 

 to its natunre to be unlimited, but because the unlimited ex- 

 istence of individuals would be a luxury without any corres- 

 ponding advantage. 



Herbert Spencer remarlis upon this : " The changes of every 

 ^ggf^gs'-Ci no matter of what kind, inevitably end in a state of 

 equilibrium. Suns and planets die, as well as organisms. " But 

 has the theory been proved, either by thehistologist, themicro- 

 sccpist, or the chemist ? Spencer presses the point that the 

 immortality of the protozoa has not been proved. And, after 

 all, when Weismann makes the continuity of the germ plasm 

 the foundation of a theory of heredity, he is building upon a 

 pure hypothesis. 



From the continuity of the germ-plasm, and its relative 

 segregaiion from the body at large, save with respect to nutrition, 

 he deduces, a priori, the impossibility of characters acquired 

 by the body bemg transmitted through the germ-plasm to the 

 offspring. From this he implies that where we find no intelli- 

 gible mechanism to convey an imprint from the body to the 

 germ, there no imprint can be conveyed. Romanes has 

 brought forward many instances which seem to contradict this 

 theory, and Herbert Spencer remarks that "a recognised 

 jprinciple of reasoning — 'the law of parsimony' — forbids the 



assumption of more causes than aie needful for the explanation 

 of phenomena. We have evident causes which arrest the cell 

 multiplication, therefore it is illegitimate to ascribe this ant si 

 to some propetty inherent in the cells." 



With regard to the reduction or disappearance of an organ, 



he slates "that when natural selection, either direct or rcversid, 



is set aside, why the mere cessation of selection should cau-e 



decrease of an organ, irrespective of the direct effects of disease, 



I am unable to see. Beyond the production of changes in the 



size of parts, by the selection of fortuilously arising variation, I 



I can see but one other cause for I he production of ihem — ;lic 



j competition among the parts for nutriment. . . . The active 



parts are well supplied, while the inactive parts are ill supplied 



! and dwindle, as does the arm of the Hindu fakir. Tliis com- 



' petition is the cause of economy of growth — this is the cause of 



decrease from disease." 



I may illustrate Mr. Herbert Spencer's remarks by the 

 familiar instance of the pinions of the Kakapo (iVn'n^o/j) — still 

 remaining, but powerless for flight. 



As for acquired habits, such as Ihe modification of bird archi- 

 tecture by the same species under changed circumstances, how 

 they can be better accounted for than I y hereditaiy Iransini'.red 

 instinct, I do not see. I mean such cases as theground-ne-iini; 

 Diduuculus in Samoa having saved itself (rom extinction since 

 the introduction of cats, by roosting and nesting in tnxs ; or 

 the extraordinary acquired habit of ihe black-cap in the Canaries-, 

 observed by Dr. Lowe, of piercing (he calyx of Hibiscus rnsa- 

 sinensis — an introduced plant — to attract insecis, for which he 

 quietly sits waiting. So the lying low of a covey of partrirli^es 

 under an artificial kite would seem to be a transmitted insluict 

 from a far-off ancestry not yet lost ; for many generations of 

 partridges, I fear, must have passed since the last kite hovered 

 over the forefathers of an English partridge, save in very few 

 parts of the island. 



I cannot conclude without recalling that the past year has 

 witnessed the severance of the last link wiih the pe-Darwii i.iii 

 naturalists in the death of Sir Richard Owen. Though n v. r 

 himself a fieldworker, or the discoverer of a single animal \\\\ni 

 or extinct, his career extends over the whole history of ])ala;on- 

 tology. I say palaeontology, for he was not a geologist in ihe 

 1 .sense of studying the order, succession, area, struclu'.'e, and 

 I disturbance of strata. But he accumulated facts on thu fossil 

 • remains that came to his hands, till he won the fame cf being 

 the greatest comparative anatomist of the age. To him we 

 owe the building up of the skeletons of the giant Dinor.iilhiiia 

 and many other of the perished forms of the gigantic sloths, 

 armadilloes, and mastodons of South America, Australia, and 

 Europe. He was himself a colossal worker, and he never 

 worked for popularity. He had lived and worked too long 

 befoi'e the Victorian age to accept readily Ihe doctrines which 

 have revolutionised that science, though none has had a larger 

 share in accumulating the fact", the combination of which of 

 necessity produced that transformation. But, though he clung 

 fondly to his old idea of the archetype, no man did more than 

 Owen to explode the rival theories of both Wernerians and 

 Huttonians, till the controversies of Plulonians and Neptunians 

 came to us from the far past with as little to move our interest 

 as Ihe blue and green controversies of Constantinople. 



Nor can we forget that it is to Sir Richard's indomitable 

 perseverance that we owe the magnificent palace which contains 

 the national collections in Cromwell Road. For many yeirs 

 he fought the battle almost alone. His demand for a building 

 of two stories, covering five acres, was denounced as audacious. 

 The scheme was pronounced foolish, crazy, and extravagant ; 

 but, afier twenly years' struggle, he was viciorious, and in 1S72 

 the Act was passed which gave not five, but more than seven 

 acres for the purpose. Owen retired from its direction in 1883, 

 having achieved the crowning victory of his life. Looking back 

 in his old age on the scientific achievements of the past, he 

 fully recognised the prospects of si ill further advances, and 

 observed, " The known is very small compared with the know- 

 able, and we may trust in the Author of all truth, who, I think, 

 will not let that truth remain for ever hidden." 



I have endeavoured 10 show that there is si ill room for all 

 workers, that Ihe naturalist has his place, though Ihe morpholo- 

 gist and the physiologist have righlly come into far greater 

 prominence, and we need not yet abandon the field-glass and 

 the lens for Ihe microscope and the scalpel. The sludiesof the 

 laboratory slill leave room for the observations of the field. 

 The invesligalion of muscles, the analysis of brain tissue, the 



MO. 1247, VOL. 48] 



