434 E. I. WERBER 



. . . . even though the monsters resulting from the present 

 or future experiments, in which the cause is applied after the forma- 

 tion of the germ and is therefore secondary, be found upon careful 

 examination to be definite Cosmobia, it will prove only that such 

 monsters can be thus produced and not that Nature does produce 

 them in the same way. 



It is, obviously, difficult to deny the justifiability of this 

 argument, but on the other hand — I think Professor Wilder 

 will admit — it practically amounts to questioning the value of 

 many explorative experiments in biology. 



May 30, 1917. 



LITERATURE CITED 



(For a more complete list of the extensive literature on the subject the reader 

 is referred to the chapter on double monsters in Schwalbe's textbook and to 

 Hiibner's article.) 



Bataillon, E. 1901 La pression osmotique et les grands problemes de la 



Biologie. Arch. f. Entw.-Mech., vol. 11. 

 Bolk, L. 1906 Dubbelmonstra, hun Classificatie en Ontstaan. Genees- 



kundige Bladen uit Klinik en Laboratorium. 12. Reeks., Nr. 9 en 



10. Haarlem. (Quoted from Hiibner.) 

 Conklin, E. G. 1897 The embryology of Crepidula. Jour. Morph., vol. 13. 

 Driesch, H. 1893 Entwicklungsmechanische Studien. III-VI. Zeitschr. f. 



Wiss. Zool., vol. 55. 

 Fernandez, M. 1909 Beitriige zur Embryologie der Giirteltiere. Zur Keim- 



blattinversion und spezifischen Polyembryonie der Melita (Tatusia 



hybrida Dem.). Morpholog. Jahrb., vol. 39. 

 Fischel, A. 1898 Experimentelle Untersuchungen am Ctenophorenei, I-IV, 



Arch.' f. Entw.-Mech., vols. 6 and 7. 



1902 tjber den gegenwartigen Stand der experimentellen Teratologic 



Verhandlg. d. deutschen patholog. Gesellsch., Berlin, 1903. S. 255-357. 



Referat gehalten auf der 5. Tagung der deutschen patholog. Gesel- 

 lsch., Karlsbad, 22-26 Sept., ^902. 

 Gerlach, L. 1882 Die Entstehungsweise der Doppelmissbildungen bei den 



hoheren Wirbeltieren. Stuttgart. 

 Goldfarb, A. J. 1916 Experimental studies upon stale germinal products. 



Carnegie Institution of Washington. Year Book No. 14, for the year 



1915. 



1917 a Experimental studies upon the aging and death of germ-cells. 



Carnegie Institution of Washington. Year Book No. 15, for the year 



1916. 



1917 b The effects of ageing upon germ cells and their development. 



Proc. of the Society for Exp. Biol, and Medicine. Eighty-first meet- 

 ing, February 10. 



