464 



NATURE 



[August 14, 19 19 



generally nearly intermediate in character between 

 their two parents ; hut in the next generation the 

 offspring commonly revert to one or both of thetr 

 grandparents, and occasionally to more remote 

 ancestors " (vol. ii., p. 383). 



The somatic cells of the hybrid, according to the 

 theory of pangenesis, throw oh gemmules carrying the 

 character-units, and, as Darwin says, " by the same 

 hypothesis dormant gemmules derived from both pure 

 parent-forms are likewise present. . . ." 



■"Consequently," he contmues, "the sexual elements 

 of a hybrid will include both pure and hybridised 

 gemmules; and when two hybrids pair, the com- 

 bination of pure gemmules derived from the one 

 hybrid, with the pure gemmules of the same parts 

 derived from the other, would necessarily lead to com- 

 plete reversion of characters " (ibid.). 



Here we have as exact a presentation of the allelo- 

 morphic idea of homozygosis as could be wished. We 

 have merely to substitute the word " factors " or 

 •■genes" for "gemmules" to have virtually a state- 

 ment in the form of the Mendelian theory. 



Finally, Darwin says : — 



"And," lastly, hybridised gemmules derived from, 

 both parent hybrids would simply reproduce the 

 original hybrid form " {ibid.). 



Here is what appears to be, and substantially is on 

 its face, a Mendelian form of explanation of recom- 

 bination in heterozygosis, with this difference : 

 According to Darwin's conception, tlie "gemmules," 

 or as we should say "factors," come over, DrxDr, 

 from the respective parents in an already hybridised 

 state, and give rise, simply by virtue of their all being 

 there in a hybrid, to a complete bodily state of Dr 

 — the hybrid condition — not, however, by means of 

 segregation and recombination. Here is lacking, of 

 course, the conception of separation and recombina- 

 tion according to the law of chance of D and r, giving 

 I DD : 2 Dr : I rr. Such an explanation could 

 scarcely have been expected to be worked out short of 

 an expei-iment such as Mendel's, involving actual 

 counts. It does seem strange to us now, in view of 

 the several times previously recurring observations by 

 some five different breeders, including those of Goss 

 and Knight, of the phenomenon of the appearance of 

 different coloured peas in tha same pod as the result 

 of crossing, that this phenomenon should not have 

 aroused curiosity and led to experiments on Darwin's 

 part, for he refers to them all. However, in 

 view of the fact that neither Nageli nor Focke — 

 the onlv investigators before 1900 who were acquainted 

 with Mendel's papers at all— was particularly im- 

 pressed with the importance of his experiments with 

 peas, it is not surprising that Darwin should, among 

 others, have failed to find the clue that Mendel did. 



However, as a contribution to the development of 

 the historv of hybridisation, Darwin's application of 

 his doctrine of pangenesis is highly interesting, 

 showing the operation of an able mind, in the absence 

 of adequate experimental data, in framing a con- 

 ception of a theory of hybrids that comes surprisingly 

 near being a statement of the present point of view 

 as regards operation and, in the case of homozygosis, 

 in regard to theorv as well. 



Herbert F. Roberts. 



Department of Botany, Kansas State Agri- 

 cultural College, June 24. 



Wild Birds and Distasteful Insect Larvae. 



Dr. W. E. Collinge, gives in Nature of July 24 

 some most interesting details about the distastefulness 

 of insects to birds. He observes that both the larva 

 and imago of Abraxas grossiila.riata are eaten by various 

 species." I would like to add the following observa- 

 NO. 2598, VOL. 103] 



tions : — During the last few years I have bred several 

 thousand larvae, including those of A. grossulariata,. 

 in order to study their genetics. Owing to the im- 

 possibility of setting all the imagines, a certain 

 number were set free as soon as recorded. In this 

 way I have thrown out of rhy window imagines of 

 the following species : — A. grossulariata, Spilosoniu 

 mendica (larvae and imagines), and both type and 

 melanic forms of Tephrosia consonaria, Boarmia con- 

 sortaria, and B. abietaria. I have noticed the fol- 

 lowing points : — (i) The birds round the house, chiefly 

 sparrows, would eat the imagines of all five species, 

 but A. grossulariata the least readily, tearing off the 

 wings and devouring the body on the spot (it was too 

 late in the year for them to be feeding young). _ (2) My 

 larvae of S. mendica were suffering from a disease (a 

 lilter-passer, I believe, for smears revealed no micro- 

 organisms), and when an entire brood was past hope 

 I used to throw them into the garden. Some were 

 dead and many dying, but they were cleared away in 

 a few minutes, in spite of their evil smell. (3) The 

 imagines of B. consortaria and B. abietaria were 

 eaten with the utmost avidity. No sooner had one or 

 two insects been rhrown out than a number of birds 

 would crowd round waiting for the next, and if this 

 were hidden in the ivy round the house they would 

 hunt for it until it was found. On one occasion some 

 insects were hidden in a flower-pot on the window-sill, 

 but the birds soon found them, and would afterwards 

 return to the edge of the pot, as if waiting for more. 

 These birds would even carry off dry pinned insects, 

 possiblv for their nests. The fact that birds will not 

 eat A.\qrossulariata readily, but will eat the diseased 

 larv£e of 5. mendica, seepis to support Mr. Speyer's 

 view, especially since the parasites mentioned do not 

 live in the afimentary tract. For this reason they 

 contain no proteolytic enzymes, and can therefore be 

 of no conceivable harm to young birds. 



Observations as to the extent to which birds prey 

 upon tlie imagines of various species have a special 

 interest, because those theories of mimicrj' whichare 

 based on natural selection demand some conscious 

 selective agent such as birds, although there are very 

 few actual observations to support such a conclusion. 

 Evidence concerning? European species is, of course, 

 onlv of value bv analogy. H. Onslow. 



3 Selwyn Gardens, Cambridge, August 2. 



THE BRUSSELS MEETING OE THE 

 INTERNATIONAL RESEARCH COUNCIL. 



THE Inter-Allied Conference on International 

 Organisations in Science, which met in 

 Paris on November 26-29, 1918, adopted a 

 number of resolutions for constituting such organ- 

 isations for the promotion of co-operation in 

 scientific work, and appointed an executive com- 

 mittee to carry them out until the scheme was 

 sufficiently advanced for the International Council 

 to be convened and to assume its final form as 

 a federation of National Research Councils. 



This took place at a meeting which was held 

 in Brussels on July 18-28, where the following 

 countries and dominions were represented by 

 their delegates : Belgium, Canada, France, Italy. 

 Japan, New Zealand, Poland, Rumania, Serbia, 

 the United Kingdom, and the United States oF 

 America, 



On the morning of Friday, July 18, the 

 delegates met In the Palais des Academies, where 

 King Albert was present. M. Harmignie, the 



) 



