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NATURAL SCIENCE. Sept., 



or develop separately. When, however, an intermediate condition 

 exists, growth together may go on for a time. Then, after a time, the 

 twig grows rootlets for itself, which penetrate the stem of the other, 

 and, trying to achieve its own individuality, becomes a parasite 

 instead of a part of the other plant. Sometimes plants, between 

 which disharmony exists, may be brought together by a third. Thus 

 plant A, which will not groAV upon B, may have a third plant C, 

 such that when C is grafted upon the stem of A, then B can be 

 grafted upon C. 



Resembling the conditions of vegetative affinity are the con- 

 ditions of sexual union. Thus, infertility is graded from being com- 

 plete to partial. Sometimes only the first cleavage occurs ; sometimes 

 a gastrula and so forth, but death ensues from no outward cause. 



Animal parallels, such as transplantation, are rarer. Trembley 

 succeeded in cutting two specimens of Hydra fusca across and getting, 

 in one case, the cut halves of the different animals to unite. But he 

 could not graft upon Hydra part of another hydroid. 



Oilier succeeded, after removing a part of the periosteum from one 

 spot in an animal, in making it grow and become bony in another part 

 of the same animal. But it was an evanescent success, for the new 

 growth being a foreign object in its novel place, speedily became 

 absorbed. In the case of transplanting from the dog to other animals 

 like cat, rabbit, etc., either the new growth got absorbed, or it festered, 

 or became enclosed in a cyst. 



Paul Bert transplanted part of the tail of a young rat to another 

 part of the body. There it grew, all the tissues but the nervous 

 developing well. Transplantation of the tail to other animals was 

 more difficult. Usually it festered, and nearly killed the animal. 

 Sometimes it was resorbed ; only in cases of very nearly-alHed 

 animals did it grow. 



A. Schmitt recently found that pieces of skin transplanted to 

 animals of another species invariably festered out, or were quietly 

 resorbed. 



In the case of transfusion of blood, failure always was the result 

 of experiments between animals of different species. In large doses 

 it was fatal ; in small, harmful ; and always, in a very few minutes, the 

 transfused blood corpuscles began to degenerate, their haemoglobin 

 appearing in the plasma. Landois and others conclude that the 

 results of transfusion correspond with the anatomical affinities of the 

 animals experimented upon. 



Hertwig concludes that the cells, in addition to their tissue 

 characters, have species characters, and that as one can speak of the 

 sexual affinities of the sex-cells, so one can of the vegetative affinities 

 of the tissue-cells. 



Before proceeding to give an account of Hertwig's further 

 criticism of Weismann's theory of heredity, it is worth while to sum 

 up the part of the argument already treated. Upon Weismann's 



