330 THE POPULAR SCIENCE MONTHLY. 



Natural selection has accordingly acted to secure this, by render- 

 ing 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 ex- 

 cessive 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 

 Diiring'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 observa- 

 tions, 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. 



< »» 



MY SCHOOLS AND SCHOOLMASTEKS.* 



By Peofessoe TYNDALL. 



OUR lives are interwoven here below, frequently, indeed most fre- 

 quently, 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 found- 

 ing on the slope of a Swiss mountain the ^ggischhorn Hotel. The suc- 

 cess 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 perma- 

 nent 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 iEggischhorn ; without the JEggisch- 

 horn 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 



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



