THE ARCHOPLASMIC STRUCTURES 3IQ 



Boveri's celebrated archoplasm-hypothesis. Boveri has from the first 

 maintained that the amphiastral fibres are quite distinct from the Gen- 

 eral cell-meshwork. In his earlier papers he maintained ('88, 2) that 

 the attraction-sphere of the resting cell is composed of a distinct sub- 

 stance, '' arcJioplasm,'' consisting of granules or microsomes aggre- 

 gated about the centrosome as the result of an attractive force exerted 

 by the latter. From the material of the attraction-sphere arises the 

 entire achromatic figure, including both the spindle-fibres and the 

 astral rays, and these have nothing to do with the general reticulum 

 of the cell. They grow out from the attraction-sphere into the reticu- 

 lum as the roots of a plant grow into the soil, and at the close of 

 mitosis are again withdrawn into the central mass, breaking up into 

 granules meanwhile, so that each daughter-cell receives one-half of 

 the entire archoplasmic material of the parent-cell. Boveri was 

 further incUned to believe that the individual granules or archoplas- 

 mic microsomes were " independent structures, not the nodal points of a 

 general network," and that the archoplasmic rays arose by the arrange- 

 ment of these granules in rows without loss of their identity.^ In a 

 later paper on the sea-urchin this view underwent a considerable 

 modification through the admission that the archoplasm may not ])re- 

 exist as formed material, but that the rays and fibres may be a new 

 formation, crystallizing, as it were, out of the protoplasm about the 

 centrosome as a centre, but having no organic relation with the gen- 

 eral reticulum ; though Boveri still held open the possibilitv that the 

 archoplasm might preexist in the form of a specific homogeneous sub- 

 stance distributed through the cell, though not ordinarily demonstra- 

 ble by reagents.^ In this form the archoplasm-theory approaches 

 very nearly that of Strasburger, described below. 



There are three orders of facts that tell in favour of Boveri's modi- 

 fied theory : first, the existence of persistent archoplasm-masses or 

 attraction-spheres from which the amphiasters arise ; second, the 

 origin of amphiasters in alveolar protoplasm ; and, third, the increas- 

 ing number of accounts asserting the replacement of the old asters 

 by others of quite new formation. In at least one case, namely, that 

 of Noctiluca, the entire achromatic figure is formed from a permanent 

 attraction-sphere lying outside the nucleus and perfectly distinct fn^n 

 the general cell-meshwork.^ Other cases of this kind are very rare, 

 and in most cases the attraction-sphere sooner or later disintegrates,^ 

 but in the formation of the spermatozoa we have many examples of 

 archoplasmic masses (Nebenkern, attraction-sphere, idiozome), which 

 apparently consist of a specific substance having a special relation to 

 the achromatic figure. 



1 '88, 2, p. 80. 3 Ishikawa, '94, '98, Calkins. '98, 2. 



2 '95, 2, p. 40. ^ Cf. p. 323. 



