TRANSACTIONS OF SECTION D. 795 



As to cases of edible insects mimickiDg inedible, Mr. Poulton admits that even 

 unpalatable animals have their special enemies, and that the enemies of palatable 

 animals are not indetinitely numerous. 



Mr. Beddard gives tables of the results obtained by Weismann, Poulton, and 

 others, which show that it is impossible 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 Dijptera, whose larviE live on the larvas of Hymeyioptera, 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 judge, 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 bomhylans occurs in two varieties, which prey upon 

 the humble-bees, Bomhus muscoruvi and B. lajndarius, which they respectively 

 resemble. Mr. Bateson does not question the behaviour of the Volucella, but states 

 that neither variety specially represents B. muscorum, 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 illustrate mimicry, two specimens of another species, B. st/lvarum, 

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

 B. muscoruyn. 



But Mr. Hart explains the parasitism in another way. He states that a nest 

 of B. 7nuscorum 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 most resemble are irascible, and therefore more 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 in- 

 stances I have cited show that there is much reason for further careful observation 

 by the field naturalist, and much yet to be discovered by the physiologist and the 

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



I had proposed to occupy a considerable portion of my address with a statement 

 of the present position of the controversy on heredity, by far the most difficult and 

 important of all those subjects which at present attract the attention of the biolo- 

 gist ; but an attack of ilbiess has compelled me to abandon my purpose. Not that 

 I proposed to venture to express any opinions of my own, for, with such protago- 

 nists in the field as Weismann, Wallace, Romanes, and Poulton on the one side, 

 and Herbert Spencer and Hartog on the other, ' Non nostruyn inter vos tantas 

 componere litest 



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 homo- 

 geneity. 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 assumes to possess an unlimited 

 power of continuance, and that life is endowed with a fixed duration, not because 

 it is contrary to its nature to be unlimited, but because the unlimited existence of 

 individuals would be a luxury without any corresponding advantage. 



Herbert Spencer remarks upon this : ' The changes of every aggregate, 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 the histologist, the 

 microscopist, or the chemist ^ Spencer presses the point that the immortality of 

 the protozoa has not been proved. And, after all, when Weismann makes the con- 

 tinuity 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 segregation from the 

 body at large, save with respect to nutrition, he deduces, d, •priori, the impossibility 



