INTRODUCTION. 9 



elusive evidence is forthcoming to show whether this 

 substance is permanent in all cells, and whether it was 

 originally nuclear or cytoplasmic in origin, although 

 the widespread intra-nuclear condition favours the 

 view that it originated there."* 



The importance of the nucleus in the economy of all 

 unicellular organisms has been well established. With- 

 out it the function of digestion cannot take place. 

 Hofer in 1889, and Verworn later, demonstrated that 

 no digestive fluid is prepared in the cytoplasm when 

 the nucleus is absent. Hofer also held that the slimy 

 secretion by which the common Amoeba anchors itself 

 before food-taking is never formed by the enucleated 

 portions; and Verworn in 1888 showed that enucleated 

 pieces of Polystomella (one of the marine Foraminif era) 

 could not repair or regenerate the lost shell, while 

 nucleated pieces quickly repaired it. The conclusion 

 of this observer was that enucleated protoplasmic masses 

 cease entirely those chemical processes by which pro- 

 ducts of the normal shell are used or formed. The 

 generalisation may now, Calkins concludes, be made 

 that no secretion takes place in enucleated fragments. 

 On the other hand, the nucleus, by itself /. e. separated 

 from the cytoplasm has no longer the power to 

 regenerate the lost parts, and like the enucleated cyto- 

 plasm, soon dies. Biitschli's conclusion that " the 

 nucleus needs the plasm, the plasm the nucleus," seems 

 well grounded. Their activities are reciprocal. One 

 without the other cannot live. The process of secre- 

 tion, therefore, whether for the purpose of digestion, 

 or whatever else, in the life of the unicellular organism, 

 is expressed by constant chemical interchange between 

 the cytoplasm and the nucleus. 



MEANS OF LOCOMOTION. 



Except in a small number of species, the Rhizopoda 

 are endowed with the power of locomotion through 



* Op. cit., p. 278. 



