232 SOME PROBLEMS OF CELL-ORGANIZATION 



2. The Attraction-sphere 



The foregoing conception of the asters receives a strong support 

 from the study of the attraction-sphere in resting cells. It is agreed 

 by all observers that this structure is derived from the aster of the 

 dividing cell ; but there is still no general agreement regarding its 

 precise mode of origin from the aster, and the subject is confused by 

 differences in the terminology of different authors. There are some 

 cases in which the entire aster persists throughout the resting cell 

 (leucocytes, connective tissue-cells) and the term " attraction-sphere " 

 has by some authors been applied to the whole structure. As origi- 

 nally used by Van Beneden, however, 1 the word was applied (in 

 Ascaris) not to the entire aster but only to its central portion a 

 spherical mass bounded by a circle of microsomes from which the 

 astral rays proceed. At the close of division the rays fade away in 

 the general network, leaving only the central sphere containing the 

 centrosome. Boveri's account of the same object was entirely differ- 

 ent; for he conceived the attraction-sphere (" archoplasm-sphere ") 

 of the resting cell as representing the entire aster, the rays being 

 withdrawn towards the centrosome and breaking up into a mass of 

 granules. Later workers have proposed different terminologies, which 

 are at present in a state of complete confusion. Fol ('91) proposed 

 to call the centrosome the astrocentre, and the spherical mass sur- 

 rounding it (attraction-sphere of Van Beneden) the astrosphere. 

 Strasburger accepted the latter term and proposed the new word 

 " centrosphere " for the astrosphere and the centrosome taken to- 

 gether. 2 This terminology has been accepted by most botanists and by 

 some zoologists. A new complication was introduced by Boveri ('95), 

 who applied the word " astrosphere " to the entire aster exclusive 

 of the centrosome, in which sense the phrase "astral sphere" had 

 been employed by Mark in 1881. The word "astrosphere" has 

 therefore a double meaning and would better be abandoned in favour 

 of Strasburger's convenient term " centrosphere," which may be 

 understood as equivalent to the "astrosphere" of Fol. 



As regards the structure of the centrosphere, two well-marked types 

 have been described. In one of these, described by Van Beneden in 

 Ascaris, by Heidenhain in leucocytes, by Driiner and Brans in divid- 

 ing cells of amphibia, the centrosphere has a radiate structure, being 

 traversed by rays which stretch between the centrosome and the 

 peripheral microsome-circle (Figs. 34, 108, G). In the other form, 

 described by Vejdovsky in the eggs of Rhynchelmis, by Solger and 

 Zimmermann in pigment-cells, by myself in sea-urchin eggs and in 



''83, p. 548. '92, p. 51. 



