450 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ordinary sea-water, the poisonous effects of the Na ions are antagonised 

 by the presence of Ca ions and K ions, by means of which the Na ions 

 lose their poisonous nature. The reason is that these or other metal 

 ions form combinations with the proteids of protoplasm, the combi- 

 nations having different physical qualities. Muscles are contractile only 

 so long as they contain the different kinds of ions in a certain proportion, 

 and in a pure solution of sodium chloride, for example, the Ca ions and 

 K ions will gradually be replaced by Na ions, or a loss of contractility 

 supervenes. Dr. Warren's results in regard to Daphnia and the effect 

 of sodium chloride (p. 461) should be compared with these conclusions. 

 In another communication,* the author shows how this method may 

 be employed in the solution of various obscure physiological problems. 

 From the previous results it appears that irritability depends upon the 

 various ions existing in a definite proportion in the tissues. But each 

 tissue has its own specific irritability, therefore each tissue must possess 

 the various ions in different proportions — must be differently affected by 

 variation in the ions. The method can therefore be applied to the solu- 

 tion of such problems as: whether the contractions of the heart are 

 myogenic or neurogenic, for muscle or nerve-tissues contain different 

 proportions of ions, and are differently affected by added ions ; whether 

 the phenomena of cell-division are similar to those of muscular contrac- 

 tility ; what is the nature of ciliary motion ; and so on. Among the 

 results, one of extreme interest is the fact that the eggs of a marine fish 

 (Fundulus) can be made to develop and hatch in distilled water. 



Increase in the Size of the Cerebrum in Mammals.f — Prof. E. Kay 

 Lankester, starting from the fact that recent forms have a greatly in- 

 creased bulk of cerebrum as compared with their early tertiary or meso- 

 zoic fore-bears, makes the suggestion that the advantage of a larger 

 cerebral mass consists in greater " educability." " A mere spoonful of 

 cerebral tissue is sufficient to carry abundant and highly efficient in- 

 stinctive mechanisms from generation to generation ; but for the more 

 valuable capacity of elaborating new brain-mechanism in the individual 

 as the result of the individual's experience of surrounding conditions, a 

 very much larger volume of cerebral tissue is needed." It is also pointed 

 out that the capacity of learning by experience must (as it were) defeat 

 and turn from its route the otherwise triumphant transformation of 

 bodily structure. Furthermore, educability can be transmitted, being a 

 congenital character, while the results of education cannot be trans- 

 mitted. The latter have to be acquired afresh in each generation, and 

 with increased "educability"' they are more readily acquired, and a 

 larger variety of them. On the other hand, the nerve-mechanisms of 

 instincts are transmitted, and owe their inferiority, as compared with the 

 results of education, to the very fact that they are not acquired by the 

 individual in relation to his particular needs, but have arisen by selec- 

 tion of congenital variation in a long series of preceding generations. 

 Instinctive and individually acquired brain-mechanisms are in opposition 

 to one another. " The loss of instinct is what permits and necessitates 

 the education of the receptive brai,n." That instincts are due to " lapsed " 

 intelligence is a theory far removed from the truth. 



* Tom. cit., pp. 383-96. 



t Nature, lxi. (1900) pp. 624-5. Keprint from Jubilee Vol. of Soc. Biol. Paris, 

 1899. 



