ON THE MORPHOLOGICAL VALUE OF THE 

 ATTRACTION-SPHERE. 



PART I. 



PROBABLY no more rapid biological advance has ever 

 been made than that which is at present gradually 

 bringing into view the extraordinary structural complexity 

 of a single cell. The ceaseless energy with which 

 workers of all nations have attacked the cell problem will 

 leave a standing monument to the value of anticipatory 

 theories (however visionary) as a stimulus to research. 

 Indeed it is through such speculative promptings that, as 

 Whitman (i) lately put it, "all the search lights of the 

 biological sciences have been turned upon the cell. It has 

 been hunted up and down through every grade of organisa- 

 tion, it has been searched inside and out, experimented 

 upon and studied in its manifold relations as a unit of form 

 and function. It has been taken as the key to phylogeny 

 and ontogeny, and on it theories of heredity have been built." 

 Nor has the consequent increase of knowledge been con- 

 fined to any one department of cytological research ; but has 

 affected the whole range of cellular existence, beoinninor 

 in the protozoa and ending with the complex tissues and 

 formed material into which cell-structure breaks down in 

 the higher differentiation of the compound types. 



Among other things it has been made abundantly 

 evident that the rough though time-honoured division of a 

 cell merely into nuclear and cytoplasmic constituents is no 

 longer sufficient, and must be revised in accordance with 

 the study of cellular development, while it is at the same 

 time strangely interesting to see that under the influence of 

 this new study the truth of old conceptions has not been lost, 

 but reappears in the ever-increasing importance we attach 

 to the view, that all cell-structures, however complex, can in 

 their origin be resolved into nuclear and cytoplasmic deriva- 

 tives, for such a conception is now the almost universal 



