374 ^^^^ ^^^^ NUMBER OF POLAR BODIES AND [VI. 



left the equator of the spindle and have moved towards the 

 poles. In both instances the bearing upon the question would 

 be the same, for only half the number of primary loops would 

 reach each pole in either case. If therefore the primary loops 

 are not made up of identical pairs, it follows that the two 

 daughter-nuclei can only contain half the number of ancestral 

 germ-plasms which were contained in the mother-nucleus. 

 Whether the loops divide on their way to the poles or at the 

 poles themselves, no difterence will be brought about in the 

 number of ancestral germ-plasms which they contain, for this 

 number can neither increase nor diminish. The quantity of the 

 diiferent ancestral germ-plasms can alone be increased in this 

 way. I am here referring to observations made by Carnoy ^ on 

 the cells which form the spermatozoa in various Arthropods. 

 It must be admitted, however, that these divisions cannot be 

 regarded as 'reducing divisions,' if Flemming's^ suggestion be 

 confirmed, that in all these observations the fact has been over- 

 looked that the equatorial loops are not primary but secondary, 

 and that they have arisen from the longitudinal splitting of the 

 nuclear thread during previous stages of nuclear division. But 

 this point can only be decided by renewed investigation. Al- 

 though many excellent results have been obtained in the subject 

 of karyokinesis, there is still very much to be learnt before our 

 knowledge is complete ; and this is not to be wondered at when 

 we remember the great difficulties in the way of observation 

 which are chiefl}' raised hy the minute size of the objects to be 

 investigated. Flemming's most recent publications prove that 

 we are still in the midst of investigation, and that highly in- 

 teresting and important processes have hitherto escaped atten- 

 tion. A secure basis of facts is only very graduall}'^ obtained, 

 and there are still many conflicting opinions upon the details of 

 this process. I should therefore consider it to be entirely use- 

 less, from my point of view, to enter into a critical examination 

 of everything known about all the details of karyokinesis. I am 

 quite content to have shown how it may be imagined that the 

 reduction required by my theory takes place during nuclear 



' Carnoy, ' La Cytodierese chcz les Arthropodes.' Louvain, Gand, 

 Lierre, 1885. 



^ Flemming. ' Neue Bcitrage zur Kcnntniss der Zclle.' Arch. f. mikr. 

 Anat., Bd. XXIX, 1887. 



