610 MARCUS M. HARTOG. 



physiological division of labour. The meganucletjs presides 

 over the nutrition and growth of the individual, and holds the 

 power of repairing injuries ; it divides by simple constriction. 

 The MicRONucLEUs presides over the preservation of the species, 

 and is the seat of that power of rejuvenescence which allows 

 continued reproduction, and the substratum of inherited 

 qualities ; it always divides by mitosis. 



In the mitosis of the micronucleus the connecting tube of 

 the two daughter nuclei always seems to be lost by absorption 

 into the cytoplasm, and as this contains the greater part of the 

 nucleo-hyaloplasm, we may regard it as an additional proof 

 that the chromatin is the essential element of the nucleus, in 

 which reside its special functions, those of transmitting in- 

 herited properties ; while the hyaloplasm has a purely mechani- 

 cal function. The greater or lesser compensation for loss of 

 substance in mitosis is effected by osmosis only, as the nuclear 

 wall always persists. 



It is shown that fertilisation is essentially a nuclear pheno- 

 menon : the union of the chromatic elements of two nuclei of 

 different origin so as to constitute a new '^ nucleus of rejuvenes- 

 cence." As to its physiological purport, it is very obvious that 

 the common view is wrong, and that fertilisation is not neces- 

 sarily linked with multiplication. In Ciliata fertilisation 

 interrupts the ordinary rapid multiplication of the race for 

 hours and days together. Thus Onychodromus grandis 

 is six days in conjugation ; in which time by fission each 

 gamete could have produced in the thirteen bipartitions some 

 8000 offspring ; while in Vorticellines the one of the gametes 

 is practically suppressed and its power of fission annihilated. 



Rolph's theory of isophagy is only mentioned to be waived 

 as not corresponding with the facts. 



Let us now examine Weismann's view : that sexual or amphi- 

 gonic reproduction has the chief and sole function of mixing 

 inherited tendencies, and of creating individual differences, 

 through which selection forms new species. This view excludes 

 fecundation from all share in the sustenance and preservation 

 of the original species, on the ground that living matter pos- 



