DIVISION OF THE VEGETABLE CELL. 25 



takes the form of the vessel in which it is contained, bat a living 

 protoplasmic mass will never do this. An Amoeba in water, even 

 those forms which appear to have the largest proportion of the 

 medium in which they live entering into their composition, does not 

 flow over the surface of the slip upon which you place it ; it pro- 

 trudes a part of its substance, but it also retracts it ; it would just 

 as soon travel up an inclined plane or vertical surface as on a hori- 

 zontal one. Its substance is clearly under its own control, using 

 the term in its most limited sense. The protoplasm of the vegetable 

 cell is essentially similar in this respect to an Amoeba. There is 

 the same general appearance in the one as in the other. 



The outer portion of an Amoeba is, as you know, clear and hya- 

 line, all granules are absent ; and, moreover, it is evidently denser 

 than the inner portion. And this description holds as well for our 

 plant cell as for the Amoeba, only that in the former the clear outer 

 portion is far thinner, and therefore less easily seen than in the 

 latter. Still it is there, and can be without difficulty demonstrated 

 by application of a dilute acid or alcohol, which by causing the cell 

 contents to shrink, at once brings it into view. It was the clear 

 hyaline layer which the earlier observers took for a skin, and to 

 which they gave the name of Primordial utricle ; but it has now 

 long been known that it is nothing more than a denser portion of 

 the general protoplasm ; there is no line dividing it from the softer 

 parts, the density simply increasing gradually from without, in- 

 wards. In order to distinguish one from the other, the names of 

 Ectoplasm and Endoplasm have been used, but it should be clearly 

 understood that it is impossible to tell where -the one leaves off and 

 the other commences. 



Sachs says, " At the base of all protoplasmic structure there 

 probably lies a substance which is colourless, homogeneous, and not 

 visibly granular ; to it alone the name of Protoplasm ought per- 

 haps to be applied, or at all events it ought to be distinguished as 

 the foundation of protoplasm." " The fine granules which are so 

 often mingled with it are probably finely divided assimilated food 

 materials, which undergo a further chemical metamorphosis into 

 protoplasm." 



Now the question of the homogeniety or otherwise of living proto- 

 plasm is one which has been claiming and receiving great attention 

 at the hands of some of our best biologists during the last few 

 years. Dr. Be ale, for whom we must all hold great respect, has, as 



