316 RESEARCH SEMINAR. 



turtle dove (Turtur orientalis). The offspring of this hybrid, 

 mated with the domestic pigeon, exhibited segregation ; but 

 neither in the first nor the second generation were there " domi- 

 nants " and " recessives " in the Mendelian sense. 



No support was found for the so-called " principle of pure 

 germ-cells " in hybrids. Segregation is probably never com- 

 plete ; and in some cases at least the intermediate character seems . 

 to be permanent. 



August j. On the Presence of Specific Coagulins in Animal 



Tissues. By LEO LOEB. 



It has been known before that extracts of many animal tissues 

 have an accelerating effect upon the coagulation of the blood. 

 It can, moreover, be shown that there exist in animal tissues spe- 

 cific substances which act specifically upon the blood of animals 

 in which they are found, or upon the blood of related species. 

 I have previously found these specific substances in mammals, 

 birds, reptiles and amphibia. Further investigations show that 

 they exist also in invertebrates. The muscle of the lobster acts 

 more strongly upon the blood plasma of the lobster than upon 

 the blood-plasma of the blue crab ; the muscle of the blue crab 

 acts more strongly upon the blood-plasma of the blue-crab than 

 upon the blood-plasma of the lobster. Pieces of muscle of other 

 animals than arthropods, which have so far been tried, are with- 

 out effect upon the blood-plasma of the lobster. 



For vertebrate blood there exist non-specific or less specific 

 substances like peptone. Similar substances can also be found in 

 certain animal tissues. The specificity of blood-coagula of verte- 

 brates could not be demonstrated among vertebrates, although 

 they become specific if used with invertebrate blood upon which 

 they do not act at all. 



Non-specific or less specific substances exist also in inverte- 

 brate tissues, as for instance in the ova of Arbacia and other 

 animals. They are able to cause a coagulation of the blood of 

 invertebrates which are not closely related. 



The origin of these substances, which are peculiarly useful, will 

 probably have to be explained by a process of auto-immuniza- 

 tion. This explanation is suggested by the great similarity be- 



