280 J. E. S. MOORE. 



all these the resting reticulate nucleus never passes out of that 

 condition, but is constricted into two portions, each retaining 

 its original character. It does, however, as above stated, 

 bear considerable likeness to the '' Nucleolare Kernbulbirung^' 

 described by Frenzel. This latter mode of division is also 

 normal to the intestinal cells of Apus. It will, moreover, be 

 admitted that it bears a superficial resemblance to the frag- 

 mentation seen in leucocytes. But the division in these 

 elements is certainly merely a shortened-up karyokinesis, 

 accompanied by centrosomes and an archoplasmic metamor- 

 phosis, while no such structures are apparent in either intes- 

 tinal or genital cells of Apus. 



In the sense that no spindle or related parts are apparent in 

 these cells, their division approaches akinesis. In the sense 

 that all the chromatin is gathered into a single chromosome it 

 approaches karyokinesis. Monomeric (or division by single 

 chromosomes) is the best term I can devise for this method of 

 nuclear fragmentation, although of its actual affinities I am 

 still in considerable doubt. 



It is well known that in many plant forms, such as the 

 Myxomycetes, the karyokinesis, although not absent, is passed 

 through in a reduced condition, and is apparently, exclusively 

 related to spore formation ; and within the last few days Pro- 

 fessor Farmer has drawn my attention to a very remarkable 

 mode of spore formation, which he has found in certain liver- 

 worts of Ceylon, in which it is with the utmost difficulty that 

 the apparently akinetic formation of the tetrads can be shown to 

 be in reality a quadripolar karyokinesis ; and, further, it seems 

 generally agreed that such simplification is a reduction from, 

 and not an antecedent of, the more complex karyokinetic 

 division phenomena. 



Consider also the nuclear division in the Protozoa them- 

 selves. It is now known that karyokinesis of a more complex 

 order, accompanied by an enormous number of chromatic 

 bands, is normal to some Rhizopods, while in the more spe- 

 cialised and less primitive Ciliates, this phenomenon is restricted 

 to the micronuclear elements, being in them so much reduced, 



