1275 
streak, with observations on the Archenteron and Germinal Layers of Rana tem- 
poraria. Quart. Journ. N. S. Vol. XXXIL. 
ScHanz, F. 1887, Das Schicksal des Blastovorus bei den Amphibien. Jen. Zeitschr. 
Bd. XXI. 
Scorr, W. B. and H. F. OsBoRNeE, 1879, On some points in the early develop- 
ment of the common newt. Quart. Journ. Vol. XIX. 
SEDGWICK, A., 1884, On the Origin of metameric Segmentation and some other 
morphological Questions. Quart. Journ. Vol. XXIV. 
SEEMANN, J., 1907, Ueber die Entwicklung des Blastoporus bei Alytes obste- 
tricans. Anat. Hefte, 1 Abt. Bd. 33. 
SmeBoTHAM, H., 1889, Note on the fate of the blastopore in Rana temporaria. 
Quart. Journ. N. S. Vol. X XIX. 
SmitH, B. G., 1912, The embryology of Cryptobranchus alleghaniensis. Journ. 
Morph. Phil. Vol. XXIII 
Spencer, W. B., 1885, On the fate of the blastopore in Rana temporaria. Zool. 
Anz. Bd. VIII. 
Sumner, F. B., 1904, A Study of Early Fish Development. Arch. Entw. Mech. 
Bd. XVII. 
Ziecier, F., 1892, Zur Kenntnis der Oberflächenbilder der Rana-Embryonen, 
Anat. Anz. Bd. VII. 
Microbiology. — “The Enzyme Theory of Heredity.’ By Prof. 
M. W. Betertnck. 
(Communicated in the meeting of March 31, 1917). 
“Nothing is perfect at birth.” 
Combining the results of the enzymological researches of recent 
years with those obtained by the experiments on heredity, an insight 
is obtained into the nature of the horeny concerned substances which 
deserves attention. 
The most acceptable theory of heredity’ is the couception that the 
living part of the protoplasm of the cell is built up from a great 
number of factors or bearers, different from one another, which 
determine the hereditary characters of the organism; at the cell 
division these bearers double or multiply, in consequence of 
which the characters, latent or unfolded, are transferred to the 
daughter-cells. They are called: difjerirende Zellelemente (MENDEL), 
gemmules (Darwin), biophores, pangens, gens, character units, 
heredity units, MeNDELIAN factors, or factors.') 
1) G. J. MenvEL, Versuche über Pflanzen-Hybriden. Verhandl. d. naturforschenden 
Vereines in Brünn, Bd. 4, Abh. Pag 42, 8 Februar u. 8 März 1865. — C. DARWIN, 
Provisional hypothesis of Pangenesis. Domestication, Ist Ed. T. 2, Pag. 357, 1868. 
2nd Kd. T. 2, 349, 1875. — Huao pe Vries, Intracellulare Pangenesis, Jena 1889, 
and the American edition, Intracellular Pangenesis, Chicago 1910. — V. HAECKER, 
