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 amphiastcr 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 



F 



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

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

 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- 

 tcr primarily arises, may thus be variously disturbed (^r 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 sijuii/acntin of the amphiastcr, 

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

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



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. ^ '96, p. 371. 



