614 SCIENCE PROGRESS 



Finally, let me call attention to the striking illustration of 

 diffusive activity through colloid membranes and at the same 

 time of the stimulating effects produced by hormones that is 

 afforded by the observations made by Dr. Jacques Loeb, who has 

 succeeded in causing unfertilised sea-urchins' eggs to develop 

 into swimming larvae by placing them during a minute or so in 

 sea water containing a minute proportion of butyric acid and then 

 in sea water deprived of oxygen, afterwards restoring them to 

 ordinary sea water. A number of other substances have a like 

 effect. 



It is in directions such as these that inquiry is tending at the 

 present day — as it is apparent to an extent never obvious before 

 that complete understanding of the behaviour of colloids is an 

 essential preliminary to an appreciation of the chemical changes 

 which constitute life. 



I trust that I have been successful in indicating some of the 

 ways in which the foundations well and truly laid by Graham 

 are being utilised by modern builders. The scientific caution 

 which he displayed, his reticence in explaining his results, are 

 more than justified by the fact that at the present day we know 

 little more than he knew as to the precise nature of the process 

 of diffusion — though undoubtedly we begin to see our way 

 towards the light. 



We need another Graham to take up the subject afresh and 

 give us the multitude of facts that are required to make even an 

 approximate interpretation of the process possible. 



H. E. A. 



