BY W. J. BYRAM. XV 



higher organisms are aggregates of independent units, for in 

 many cases protoplasmic strands have been detected passing 

 from cell to cell. It has, therefore, been suggested that the 

 so-called multicellular animals and plants are complexes of a 

 multitude of nucleated centres all in vital inter-connection — the 

 one with the other. These inferences are not established, and, 

 if they were, they do not affect the hypothesis that the cell units 

 are delicate life machines. It is apparent that in unicellular 

 animals and plants the unit exists j)t'r se, and in many instances 

 cells detached from multicellular animals and plants can con- 

 tinue their life either indefinitely or for a time. The ciliated 

 epithelial cells, which may be obtained by scraping a frog's 

 throat, have all the appearance of infusorial animalcubf. They 

 are nucleated cells, and, when detached, they can swim about for 

 a time by means of their processes, and lead an independent life. 

 Again, in the zoophytes, — those minute organisms which are 

 found in rock pools left by the receding tide — each unit, or 

 " zooid," as it is called, although in organic connection with the 

 stalk, which is the common base of all, and thus united with the 

 others in a colony, is a distinct animalcule, and may be detached 

 and live a separate life. The volvox globator affords another 

 example of the inter-connection of the cell units. It is a minute 

 colony of plant cells, united so as to form a bright green globule, 

 just visible to the naked eye, moving through the water in which 

 it lives by means of the combined ciliary action of the cells. If 

 while under examination, the cells are carefully focussed with 

 the fine adjustment of the microscope, they are found to be 

 united, giving rise to a delicate hexagonal appearance over the 

 surface of the sphere. But it will be found that certain of the 

 cells enlarge and subdivide, and finally detach from the mother 

 sphere internally, and by repeated subdivisions develop into new 

 spheres. Thus, while there is an inter-connection of cells 

 in the multicellular plants and animals, and it is probably a 

 misconception to regard such organisms as mere cell aggregates 

 or complex groups of independent units, it would be no less a 

 misconception to consider that the significance of the unit had 

 disappeared. We might as well declare that because we have a 

 centre of social activity in Sydney and another in Brisbane, the 

 connection of the two by a line of railway obliterates the 

 position of both as independent communities. In accordance, 

 therefore, with the hypothesis which now prevails, the cell is a 

 very delicate piece of mechanism of vast complexity. It is 

 supplied with fuel in the shape of nutrient material, and by the 



