3 24 SOME PR OBLEMS OF ' CELL- OR GANIZA TION 



takes up such a position as to pass entirely into one of the grand- 

 daughter-cells, while the new sphere-substance is equally distributed 

 between them and in its turn passes into one of the cells of the en- 

 suing division. 1 



In Crepidula, as in Ascaris, the attraction-sphere represents only 

 the central part (centrosphere) of the aster. In some cases, however, 

 e.g. in leucocytes, the entire aster may persist, and the term attrac- 

 tion-sphere has by some authors been applied to the whole structure. 

 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 surrounding it 

 (attraction-sphere of Van Beneden) the astrosphere. Strasburger 

 accepted the latter term but proposed the new word centrosphere 

 for the astrosphere and the centrosome .taken together. 2 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 centro- 

 sphere, which may be understood as equivalent to the " astrosphere " 

 of Fol. 



Besides these terms we have Heidenhain's microcentrum (p. 311), 

 equivalent to the centrosome or group of centrosomes at the centre of 

 the aster, with its surrounding sphere ; 3 Kostanecki's and Siedlecki's 

 microsphere, applied to the central region of the aster surrounding the 

 centrosome whether bounded by a distinct microsome-circle or not ; 4 

 Erlanger's centroplasm, equivalent to microsphere ; 5 Ziegler's ecto- 

 sphere and entospJiere, applied to the cortical and medullary zones 

 respectively ; and Meves's idiozome, applied to the " attraction-sphere " 

 of the spermatids. 6 This profusion of technical terms has arisen 

 through the desire to avoid ambiguity in the use of the term " attrac- 

 tion-sphere," which, like the word " Nebenkern " (p. 163), has been 

 applied to bodies of quite different origin and fate. If we adhere to 

 Van Beneden's original use of the term it must be confined to the body 

 surrounding the centrosome, forming a part of, or directly derived 

 from, an aster, and giving rise wholly or in part to the succeeding aster. 

 Meves ('96), Rawitz ('96), Erlanger ('97, 2), and others have, however, 

 clearly shown that the "attraction-sphere" surrounding the centro- 

 some (in testis-cells) may not only contain other material derived from 

 the cytoplasm, e.g. the " centrodeutoplasm " of Erlanger, but may 

 take no direct part in the succeeding aster-formation, disintegrating 

 and scattering through the cell as the new aster forms (Fig. 27). In 



1 Cf. p. 424- 3 '94, P- 463- 6 '96, 3, P- 8. 



2 '92, p. 5. 4 '96, p. 217. 



