FIELD STUDY IN ORNITHOLOGY. 481 



Mr. Beddard gives tables of the results obtained by Weismaim, Poul- 

 ton, and others, which show that it is impossible to lay down any defi- 

 nite 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 Voliicella, 

 a genMS of Diptera, whose larvae live ou the larvie of Hymenopter a, and 

 of which the perfect insect closely resembles some sj)ecies 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 ento- 

 mologist can judge, proves that while there is much that can be explained 

 by mimicry, there is, nevertheless, a danger of its advocates ju'essing it 

 too far. Yolucella homhylans occurs in two varieties, which prey uijon 

 the humble-bees, Bomhus nniscormn and B. lapidarius, which they 

 respectively resemble. Mr. Bateson does not question the behavior 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 mining, two specimens of another species, B. si/lvarmn, were 

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

 labeled B. muscorum. 



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

 that a nest of B. nmscorum is made ou the surface, without much 

 attempt at concealment, and that the bee is a peculiarly gentle species, 

 Avith 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 Yolucella should mimic the 

 bee, which it does not affect, more closely than the one which is gener- 

 ally 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 naturalist, and much yet to 

 be discovered by the physiologist and the chemist, as to the composi- 

 tion and nature of animal pigments. 



HEREDITARY ACQUISITIONS. 



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 biologist; but an attack of ill- 

 ness has compelled me to abandon my purpose. Not that I proposed 

 to venture to express any opinions of my own, for with such prota- 

 gonists in the field as Weisman, Wallace, Romanes, and Poultou on 

 the one side, and Herbert Spencer and Hartog on the other, " Non noa 

 trum inter vos tantas componere liieHP 



So far as I can understand Weisman's theory, he assumes the separa- 

 tion of germ cells and somatic cells, and that each germ cell contains 

 SM 93 31 



