3l6 SOME PROBLEMS OF CELL-ORGANIZATION 



of Euglena and Amoeba and the sphere of Noctiluca and Paramoeba are to be com- 

 pared with the attraction-sphere, while the centrosome may have had a different 

 origin. 



It appears to me that none of these views rests upon a very substantial basis, and 

 they must be taken rather as suggestions for further work than as well-grounded 

 conclusions. 



F. THE ARCHOPLASMIC STRUCTURES 

 I. Hypothesis of Fibril lar Persistence 



The asters and attraction-spheres have a special interest for the 

 study of cell-organs ; for they are structures that may divide and 

 persist from cell to cell or may lose their identity and re-form in suc- 

 cessive cell-generations, and we may here trace with the greatest 

 clearness the origin of a cell-organ by differentiation out of the struc- 

 tural basis. Two sharply opposing views of these structures have 

 been held, represented among the earlier observers on the one hand 

 by Boveri, on the other by Biitschli, Klein, Van Beneden, and Carnoy. 

 The latter observers held that the astral rays and spindle-fibres, and 

 hence the attraction-sphere, arise through a morphological rearrange- 

 ment of the preexisting protoplasmic meshwork, under the influence of 

 the centrosome. This view, which may be traced back to the early 

 work of Fol ('73) and Auerbach ('74), was first clearly formulated 

 by Biitschli ('76), who regarded the aster as the optical expression of 

 a peculiar physico-chemical alteration of the protoplasm primarily 

 caused by diffusion-currents converging to the central area of the 

 aster. 1 An essentially similar view is maintained in Biitschli's recent 

 great work on protoplasm, 2 the astral " rays " being regarded as 

 nothing more than the meshes of an alveolar structure arranged 

 radially about the centrosomes (Fig. 10, B). The fibrous appearance 

 of the astral rays is an optical illusion, for they are not fibres, but flat 

 lamellae forming the walls of elongated closed chambers. This view 

 has recently been urged, especially by Erlanger ('97, 4, etc.), who 

 sees in all forms of asters and spindles nothing more than a modified 

 alveolar structure. 



The same general conception of the aster is adopted by most of 

 those who accept the fibrillar or reticular theory of protoplasm, the 

 astral rays and spindle-fibres being regarded as actual fibres forming 

 part of the general network. One of the first to frame such a con- 

 ception was Klein ('78), who regarded the aster as due to "a radial: 

 arrangement of what corresponds to the cell-substance," the latter 



1 For a very careful review of the early views on this subject, see Mark, Lintax, 1881. 

 2 '92, 2, pp. 158-169. 





