. 392 Charles R. Stockard. 
considerable period of time is necessary for the Mg to act upon the 
substances of the embryo and influence the origin of the optic 
vesicles. When an insufficient time intervenes between the 
period at which the eggs are subjected to the action of the solu- 
tion and that at which the optic vesicles are given off from the 
brain the Mg is unable to influence the tissues so as to induce the 
eyclopean condition. 
The production of cyclopia by the action of Mg at such late 
stages in development proves beyond doubt that this deformity 
is due to the action of external or environmental conditions on 
the developing animal. Any explanation of cyclopia based on 
germinal hypothyses such as that recently advanced by H. H. 
Wilder must: be reconstructed so as to conform to these facts. 
Accepted by the Wistar Institute of Anatomy and Biology January 12, 1910. Printed June 21, 1910. 
BIBLIOGRAPHY 
GeEMmMEL, J. F. On cyclopia in osseous fishes. Proc. London Zodél. Society, i, pp. 
1906 443-449, 
1906b Notes on supernumerary eyes, and local deficiency and reduplication 
of the notocord in trout embryos. Proc. London Zoél. Society, 1, 
pp. 449-452. 
Harrison, R. G. Embryonic transplantation and the development of the ner- 
1908 vous system. Anat. Record, i, pp. 385-410. 
Lewis, W. H. Experimental evidence in support of the theory of outgrowth 
1907 of the axis cylinder. Am. Jour. Anat. vi, pp. 461-472. 
1909 The experimental production of cyclopia in the fish embryo (Fun- 
dulus heteroclitus). Anat. Record, iii, pp. 175-181. 
Mau, F. P. A study of the causes underlying the origin of human monsters. 
1908 Jour. Morph. xix, pp. 1-861. 
Mayer, A. G. Rhythmical pulsation in seyphomedusae. Carnegie Institute of 
1908 Washington, Pub. No. 102, pp. 118-131. 
Paoxuuccr, L. Sopra una Forma Mostruosa dela Myliobatis Noctula. Atti della 
1874.  societa Italiana di Sc. Naturali. xvii, pp. 60-63. 
SrockarD, C. R. The development of Fundulus heteroclitus in solutions of lith- 
1906. ium chlorid, with appendix onits development in fresh water. Jour. 
Exp. Zo@l., iii, pp. 99-120. 
1907 The influence of external factors, chemical and physical, on,the 
development of Fundulus heteroclitus. Jour. Exp. Zodl., iv; pp. 
165-201. 
1909 The development of artificially produced cyclopean fish, ‘the mag- 
nesiumembryo.’’ Jour. Exp. Zodél., vi, pp. 285-338. 
1909b The origin of certain types of monsters. Am. Jour. Obstetrics. 
lix, no. 4. 
Witprr, H. H. The morphology of cosmobia. Am. Jour. Anat., viii.pp. 355- 
1908 440. i 
