1913] Biology of May-flies. 375 



In these two studies he followed individuals through twenty- 

 three successive moults, tracing them to the adult stage. He 

 did not, however, begin his observations at the actual time 

 of hatching as Burmeister had done. 



Hagen, 1849-1890. The foundation for the study of 

 May-flies in North America was made largely through the 

 inspiration and contributions of Prof. Hermann Hagen. Al- 

 though the greater part of his work was systematic, the notes 

 which he sent to Eaton in 1873 show that he made valuable 

 additions to the knowledge of their biology. Hagen identified 

 the nymph of Baetisca which B. D. Walsh described in 1864. 



Walsh, 1864. Walsh concluded his paper on Baetisca 

 with a description of the swimming habits of the nymphs which 

 he kept for some time under observation. 



Eaton, 1870. About the end of 1870, Rev. A. E. Eaton 

 submitted to the Entomological Society of London the most 

 important work done upon the group since Pictet's monograph. 

 In 1883-86, the completed work was published in the Trans- 

 actions of the Linnean Society. 



Eaton, 1883. In this work the world fauna was reclassified 

 and a great number of forms were described and figured with 

 such accuracy that it at once became and has remained the 

 most important work upon the order. The introduction 

 contained . a general account of the biology which included 

 several of Dr. Hagen's* field notes. 



N. Joly, 1876. Joly, '76, studied the embryology of Pal- 

 ingenia virgo. He kept eggs in dishes of water and recorded 

 the structures of the developing embryo on the 5th and 6th 

 day. This work was followed by another by N. and E. Joly, 

 which dealt mostly with the structure of the systems in the 

 nymphal and imago stages of certain species. 



Vays sieve, 1882. Vayssiere published the first extensive 

 study of the nymphs. This paper was written almost entirely 

 from a morphological view point, but it contains many refer- 

 ances to short biological papers. 



The papers of Zimmerman, '79, Eaton, Hagen, Joly, Palmer, 

 '83, Creutzburg, '85, and others were mainly morphological. 



"1873. Hagen Notes on the Ephemeridae. Compiled by Eaton. 



