392 
tion. If the heart is formed, although it pumps no blood, the embryo may 
remain alive for a considerable period, yolk absorption taking place to a 
varying degree. If the heart handles blood and bloodvessels are differen- 
tiated, the embryo is likely to develop to the point of hatching. 
7. The numerous abnormalities appearing in the hybrid embryos are 
due to a deterioration in the developmental processes, resulting probably 
from the poisonous action of the sex products upon each other. 
8. The success of the hybrids, i. e., the stage to which any given 
hybrid will develop, is correlated with the nearness of relationship of the 
two species used. 
9. The mixing of unrelated sex products is looked upon as analogous 
to the transfusion of unrelated bloods, the more distantly related the two 
species concerned the greater their toxidity. 
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Appelloff. 1894. Ueber einige Resultate der Kreuzungsbefruchtung 
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Born, G. 1885. Beitruge zur Bastardirung zwischen den einheimischen 
Anurenarten. Pfliiger’s Archiv, Bd. 32, pp. 453-518. 
Buller, A. H. Is Chemotaxis a Factor in Fertilization of Animal Eggs? 
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Driesch, H. 1898. Ueber rein-mutterliche Charactere an Bastardlarven 
von Echiniden. Roux Archiv, Bd. 7, pp. 65-102. 
Dungern, E. F. von. 1901. Die Ursachen der Specificitiit bei der 
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Dungern, E. F. yon. 1901. Neue Versuche Zur Physiologie der 
Befruchtung. Zeitsch. f. Algmein, Physiol. Bd. 1, pp. 34-55. 
Fischel. 1906. Ueber Bastardierungsversuche bei Echinodermen. 
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Friedenthal, H., und Lewandowsky, M. 1899. Ueber das Verhalten des 
tierischen Organisimus gegen fremdes Blutserum. Arch-f-Anat. u. Phys.. 
Phys. Abt., pp. 531-545. 
Guyer, M. 1900. Spermatogenesis of Normal and of Hybrid Pigeons. 
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Kammerer, P. 1907. Bastardierung von Flussbarsch (Perea fluvia- 
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Landois. 1875. Die Transfusion des Blutes. Leipzig. 
