500 Descendenz und Hybriden. — Physiologie. 



of diverse individuals and the prepotency of new variations 

 are the constructive factors, not heredity and environment, 



Symbasis is the method, interbreeding the means , and 

 sexuality the mechanism whereby organic evolution has been 

 accomplished; these are the concrete and efficient causes of 

 the vital motion of species. The association of organisms into 

 species of similar individuals is not brought about by a prede- 

 termining hereditary mechanism, but by symbasic interbreeding. 

 The highest Organization has not been attained in asexual 

 generations, but in structures completely and essentially sexual, 

 l3uilt whoUy of conjugating cells. There has been no evolution 

 away from sexuality. Long-continued violations of the law of 

 symbasis bring only degeneration. 



This interpretation of evolutionary facts opens the way to 

 an adequate physiological explanation of the significance of sex, 

 and affords also a working theory of the chief cytological com- 

 plications that have arisen as a consequence of sex — compli- 

 cations that have hitherto rendered obscure the nature of the 

 cell-bodies of higher animals and plants. 



The external diversity of organic nature and the internal 

 diversity of cells and of reproductive processes täke on new 

 and unexpected significance. Both are shown to be conse- 

 quences of sexual specialization, without which no evolutionary 

 advance beyond simple-cell colonies has been possible. More 

 than this, gradations in the perfections of the higher double- 

 celled structure are correlated with definite stages of evolutio- 

 nary progress, so that from the structure of an organism its 

 kind of sexuality can be deduced. Evolution becomes, in the 

 new view, a physiological rather than a morphological process, 

 since the methods of descent affect the quality and efficiency 

 of the organism even more promptly and fundamentally than 

 they do its external form." Trelease. 



Jaccard, P., Influence de la pression des gaz sur la 

 croissance des vegetaux. Nouvelles recherches. 

 (Verh. d. Schweiz, naturf. Gesellsch. Winterthur. 1904 [ersch. 

 1905]. p. 50—51.) 



L'auteur, en se servant de cloches de verre de 55 cm. de 

 hauteur et d'une contenance de 33 litres, a entrepris une serie de 

 cultures dans I'air deprime ä une demie atmosph. environ (30 — 40 

 cm. Hg) dans le but de contröler les r^sultats de ses premieres 

 recherches critiquees par 0. Richter dans „Bericht, d. 

 deutsch, bot. Gesellsch. Mars 1903". 



Richter, sans avoir d'ailleurs repete les exp^riences de 

 Jaccard, attribue l'accel^ration de croissance dans I'air deprime 

 au fait que les plantes en question etaient soustraites ä l'influence 

 pernicieuse de I'air du laboratoire toujours plus ou moins 

 Charge de gaz d'^clairage et de vapeurs acides ou mercurielles. 



