THE MECHANISM OF MITOSIS 



109 



and Gallardo ('96, '97). It is impossible to regard this analogy as 

 exact ; first, because it is inconsistent with the occurrence of tripolar 

 astral figures ; second, as Meves has recently urged ^ the course of the 

 astral fibres does not really coincide with the lines of force, the most 

 important deviation being the crossing of the rays opposite the equa- 

 torial region of the spindle, which is impossible in the magnetic or 

 electric field. We must, however, remember that the amphiaster is 

 formed in a viscid medium, that it may perform various movements, 

 and that its fibres probably possess the power of active growth. The 



c 



B 



D 



P 



Fig. 53. — Division of dispermic eggs in sea-urchin eggs, schematic. [BOVERI.] 



A. C. E. Eggs before division, showing various connections of the asters. D. D. F. ResuH- 



ing division in the three respective cases, showing cleavage only between centres connected by a 



spindle. 



physical or chemical effect of the centres, through which the amphias- 

 ter primarily arises, may thus be variously disturbed or modified in 

 later stages, and the crossing of the rays is therefore not necessarily 

 fatal to the assumption of dynamic centres. Biitschli ('92, '98) has, 

 moreover, recently shown that a close simulacriini of the amphiaster, 

 showing a distinct crossing of the rays, may be produced in an arti- 

 ficial alveolar structure (coagulated gelatine) by tractive forces cen- 



pended in spirits of turpentine (a poor conductor) between two electric poles. This experi- 

 ment, devised by Faraday, has recently been applied by Gallardo ('96, '97) to an analysis 

 of the mitotic figure. 1 '96, p. 371. 



