BIOPLASM AND ITS DEGRADATION. 



THOSE marvellous progressive changes which occur 

 during the development of the embryo, while the 

 structures which characterise the organism are being 

 evolved, are still but very imperfectly understood. 

 We know, indeed, that all the complex tissues and 

 organs of man and the higher animals are dependent 

 for their production upon changes occurring in a 

 minute mass of perfectly colourless living matter, in 

 which no indications of form or structure can be dis- 

 cerned, but how these changes are brought about we 

 have not yet been able to ascertain ; nor is it con- 

 veying much information to the student if the teacher 

 informs him that the perfect organism, with all its 

 marvellous apparatus, existed " potentially " in the 

 little colourless living embryonic particle, since it 

 would be impossible to distinguish the particle which 

 was to develop a highly elaborate mechanism from 

 that which was to produce a simple amoeba, as its 

 highest developmental product. Hence, while it can- 

 not be said that the structures evolved " existed " in 

 the original mass of living matter it will not make the 

 assertion more correct if it be qualified by the term 

 " potentially." All we know is that such and such 

 structures result, but we know this from seeing them, 

 not from & priori reasoning. For the characters and 



