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 degi^ee. If the heart handles blood and bloodvessels are differen- 

 tiated, the embrj'o is likely to develop to the point of hatching. 



7. The numerous abnorinalities appearing in the hybrid embryos are 

 due to a deterioration in the developmental proc-cases, 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. 



LITERATURE CITED. 



Ackerman. K. 1898. Tierbastarde Theil 2. Die AYirbelthiere. Kassel. 



Appelloff. 1894. Ueber einige Resultate der Kreuzungsbefruchtung 

 bei Knochenfischen. Bergens Museum Aarbog, Xo. 1, pp. 1-19. 



Born, G. 1883. Beitrage 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? 

 Quart. Journ. Mic. Soc, Vol. 46. 



Driesch. H. 1898. Ueber rein-mutterliche Charactere an Bastardlarven 

 von Echiniden. Roux Archiv, Bd. T, pp. 65-102. 



Dungern, E. F. von. 1901. Die Ursachen der Spec-ificitilt bei der 

 Befruchtung, Centralbl. f. Physiol. Bd. 15. pp. 1-4. 



Dungern. E. F. von. 1901. Xeue Tersuche Zur Physiologie der 

 Befruchtung. Zeitsch. f. Algmein, Physiol. Bd. 1, pp. 34-55. 



Fischel. 1906. Ueber Bastardieruugsversuche bei Echinodermen. 

 Roux' Archiv. Bd. 22, pp. 498-525. 



Friedenthal, H., und Lewandowsky, M. 1899. Ueber das Verhaiten des 

 tierischen Orgauisimus gegen fremdes Blutserum. Arch-f-Anat. u. Phys., 

 Phys. Abt., pp. 531-545. 



Guyer, M. . 1900. Spermatogenesis of Normal and of Hybi'id Pigeons. 

 Chicago, Ills. 



Kammerer, P. 1907. Bastardierung von Flussbarsch (Perca fluvia- 

 tilis) und Kaulbarsch (Acernia cernua) Roux' Archiv. Bd. 23, pp. 511-550. 



Landois. 1875. Die Transfusion des Blutes. Leipzig. 



