60 Physiologie der Zellen, Gewebe und Organe. 



(3) the early development of rudiments until they are useful. Physiology throws 

 light on such questions. 



In the evolution of animals two general movements may be observed: (1) a 

 spreading out or diversification, (2 ) a progression f orwards. These two movements 

 are at right angles, and Darwin dealt chiefly with the first, namely that which 

 gives rise to genera, species and varieties. The second movement is towards con- 

 sciousness, and culminates in man, The Suggestion is made, that these two move- 

 ments may be due to the natural selection of two different kinds of adaptations: 

 (l) adaptations of form and function to various environments, (2) the natural se- 

 lection of the function of irritability, or adaptation to changeableness of envi- 

 ronment, These two kinds of adaptations may go on at different rates in different 

 cases, and thus some simple organisms may persist unchanged for long periods 

 in special environments, while others have, through selection of the adaptation 

 of adaptability, moved rapidly forward. 



Irritability, or response by adjustment to the environment, is the most pro- 

 minent function of protoplasm and has been of predominent importance in evo- 

 lution. If natural selection is true, this response must lead to the perfecting of 

 the function. All the great mechanisms of the body are for the purpose of se- 

 curing adaptability to a variety of environments, so that finally superiority over 

 the environment is secured. A number of complex physiological mechanisms, such 

 as heat-regulation, immunity, independance of moisture, the alimentary mecha- 

 nism and the nervous system, have been gradually evolved in this way. 



Internal secretions which correlate and control the activities of organs are 

 a means of explaining the steady development of rudiments. Most of the clia- 

 racters of the human body which have steadily developed from the fishes to man 

 are dependant on the previous development of the ductless glands. All parts of 

 the organism are thus correlated in activity, the body is a unit, and a unit- 

 character, even a pigment character, cannot be an independent variable within 

 the organism or the cell. 



The various physiological changes are pointed out, by means of which raam- 

 mals came to have an advantage over reptiles in greater independance of en- 

 vironment. Gates (London). 



155) Andre, G., Sur la migration des elements mineraux et sur le deplace- 

 ment de ces elements chez les feuilles immergees dans l'eau. In: C. R. Acad. 

 des Sc. de Paris, Bd. 156, Heft 7, S. 564—566, 1913. 



Les phenomenes d'bydrolyse que subissent les feuilles fraicbes immergees dans l'eau, 

 additionnee de quelques gouttes de formol, resolvent peu ä peu, en elements plus simples, 

 les principes immediats que ees feuilles contiennent ä Fetat normal, et ces Clements 

 passent alors dans le liquide qui les entoure. 



En cons^quence de ces phenomenes, les feuilles qui tombent ä l'automne peuvent 

 restituer au sol, dans un espace de temps assez court, la majeure partie de Facide phos- 

 phorique, et la presque totalite de la potasse qu'elles avaient immobilises durant leur 

 developpement. 



L'auteur a etendu ses recherches ä tous les elements normaux de la feuille. La 

 chaux est l'element salin qui resiste le mieux a Fexosmose, le cinquieme seulemeut de 

 ce Corps a passe dans le liquide Interieur, alors que Texosmose de la magnesie a ete 

 plus considcrable. L'elimination de l'acide sulfurique est comparable ä celle de Faoide 

 phosphorique, comme si la majeure partie du soufre et du phosphore etait engagee, a 

 toutes les periodes de la Vegetation, dans des combinaisons salines facilement dialysables 

 apres la mort de la feuille. C. L. Gatin (Paris). 



156) Andre, G., Sur l'evolution des principes mineraux et de l'azote 

 chez quelques plantes annuelles. In: C. R. Acad. des Sc. de Paris, Bd. 156, 

 Heft 15, S. 1164—1167, 1913. 



