Page:Popular Science Monthly Volume 26.djvu/344

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Natural selection has accordingly acted to secure this, by rendering the offspring of a cross more able to resist an unfavorable change in the conditions of life than the offspring of closely related parents or the parthenogenetic children of unfertilized females, and the excessive birth of males, under unfavorable conditions, is for the purpose of securing variation, rather than the prevention of interbreeding.

In conclusion, I wish to again call the attention of the reader to Düring's papers, as they are filled with interesting reflections and suggestive observations which have received no notice in this short review.

They not only contain a treasury of facts, but they also show that in many parts of the field there is a great lack of recorded observations, and as some of our readers may be able to contribute something toward filling these gaps, and thus to extend our knowledge of the subject, the writer of this review takes this occasion to ask all who have made any observations upon the number of male and female births of wild or domesticated animals to make their results known. If they are sent to him, he will take pleasure in tabulating them, and will give proper credit for them.

By Professor TYNDALL.

OUR lives are interwoven here below, frequently, indeed most frequently, without our knowing it. We are in great part molded by unconscious interaction. Thus, without intending it, the present representative of the Birkbeck family in Yorkshire has helped to shape my life. In 1856, or thereabout, Mr. John Birkbeck aided in founding on the slope of a Swiss mountain the Æggischhorn Hotel. The success of this experiment provoked in the neighboring commune a spirit of rivalry and imitation, and accordingly upon a bold bluff overlooking the Great Aletsch glacier was subsequently planted the Bel Alp Hotel. To the Bel Alp I went in my wanderings. Seeing it often, I liked it well, until at length the thought dawned upon me of building a permanent nest there. Before doing so, however, I imitated the birds, chose and was chosen by a mate who, like myself, loved the freedom of the mountains, and we built our nest together. From that nest I have come straight to the Birkbeck Institution, so that the following chain of connection stretches between Mr. John Birkbeck and me: Without him there would have been no Æggischhorn; without the Æggischhorn there would have been no Bel Alp; without Bel Alp there would have been no Tyndall's nest, and without that nest the person who now

  1. An address delivered at the Birkbeck Institution, Wednesday, October 22, 1884.