378 The Unity of the Organism 



tinous material and in the center a fine axial filament. As 

 shown in figure 24, the tubes and the radial pieces are not 

 in uninterrupted continuity at the nodal points but meet 

 one another in a common joint. 



The entire skeleton is embedded in the extra-capsular sub- 

 stance, and the central capsule, figure 22, c. cap., contain- 

 ing the nucleus is, as in most Radiolaria, relatively quite 

 small. The pattern of the skeletal net Hacker conceives 

 to be determined by "directing centers," one for each of 

 the nodal points. 



This conception is, as Hacker fully recognizes, purely 

 hypothetical, and consequently ought not, in the strict 

 letter of the formulation, to be made much of. Nevertheless 

 certain of the facts call for something of the sort, if an 

 explanation of the peculiar skeletal features in accordance 

 with the principles of heredity is insisted upon. The follow- 

 ing quotation brings out the most salient of these facts : "In 

 the stereometric 'dissimilarity' which may exist between the 

 external body- and skeletal-form and the shape of the cen- 

 tral capsule ... it is difficult to imagine that the locations 

 of the nodal points, especially in the regular triangular 

 and quadrangular conditions, are determined (projected 

 outward) by the nucleus. Rather one ought to think here 

 of distributing and arranging processes which have their 

 seat in the external layers of the sarcode body itself and 

 are conditioned either by the competition (Konkurrenz- 

 kampf) of the pseudopodia or by the interplay of 'spheres 

 of attraction.'' (Hacker's Monograph, Lief. 3, p. 627.) 



Whether "directing centers" are the right things to conceive 

 as "explaining" such a skeleton as that before us may be ques- 

 tioned ; but I do not see how it is rationally possible to avoid 

 believing that the main seat of the forces at work is in the 

 extra-capsular part of the animal., as Hacker says, and not in 

 the nucleus, and that these forces are hereditary forces. And 

 such belief is the more unescapabk by the facts that, as Hacker 



