344 THE president's address. 



matter. The fluid nature of protoplasm is seen from a variety 

 of facts that can be observed without diflficulty ; chief amongst 

 these are its streaming and flowing movements and the tendency 

 of masses of pure protoplasm to round themselves off and 

 become spherical when they come to rest. Small masses of 

 protoplasm like an amoeba assume a shapeless, irregular and 

 changeable form when in movement; but when their activity 

 ceases from any cause, they become spherical in form. In such 

 organisms a definite, constant and characteristic body-form can 

 be maintained only by the formation of firm structures which act 

 like a primitive type of supporting skeleton, and which have the 

 form either of internal rods or bars or of an external envelope 

 like a skin. A further indication of the fluid nature of proto- 

 plasm is seen in the fact that drops of watery fluid, so-called 

 vacuoles, suspended in the protoplasm, tend always to have a 

 spherical form unless there is something to prevent this 

 tendency. 



The minute structure and physical nature of protoplasm is a 

 disputed subject which it is not necessary for me to discuss in 

 detail. Any one who has looked at an amoeba under a microscope 

 of even moderate magnifying power knows that its body consists 

 of a fluid ground-substance or matrix in which numerous granules 

 are imbedded. As regards first of all this matrix, the views of 

 experts are at variance ; some consider it to be a homogeneous 

 colloid fluid, but the majority of investigators hold that it 

 consists of two parts, a delicate framework and a watery cell- 

 sap. From the fluid condition of the protoplasm as a whole it 

 follows that both framework and cell-sap must be fluid ; they 

 must then be regarded as two fluids which will not mix with 

 one another. The framework is more viscid, and probably con- 

 sists of albuminous substance; the cell-sap is more fluid, and 

 appears to consist of water containing salts and substances of 

 various kinds in solution. 



It is to the granules that I must direct your attention more 

 particularly. In any sample of protoplasm there are a great 

 many diflerent kinds of granules, as shown by their reactions to 

 chemical reagents and stains. Many of the granules un- 

 doubtedly represent stages in the process of metabolism described 

 above ; that is to say, they are substances which are either on 

 their way to be built up into the complex material of the 



