Ill DIFFERENTIATION 99 



sich also der speziellere hervor '. It is also in accord with 

 the hypothesis put forward above that the various determinants 

 comprised in the chromosomes will only be able to become 

 active under the influence of different parts of the cytoplasm 

 only, that is, after the nuclei have been distributed during 

 segmentation. 



Further, early characters, such as the rate of cleavage, are 

 known to be sometimes transmitted by the male cell as in 

 hybrids of Fundulus (Newman) ; the rate may very well 

 depend on the male centrosome, but that is of nuclear origin 

 though not derived from the chromosomes. 



It seems preferable therefore to base the distinction between 

 the parts played by the two germ-cells in inheritance on the 

 magnitude of the characters concerned. 



The cytoplasm may of course carry some specific characters, 

 such as the pigment of the egg and of the embryo, for instance 

 in Amphibia ; the cuticle, which may persist as that of the 

 larva in Polychaets and the size of the egg, which may be 

 correlated with that of the embryo, though this last is not 

 necessarily so, since Conklin has found that the larger species 

 of Crepidula usually have the smaller eggs. 



It is to be observed that the characters which common 

 experience and the experiments of breeders and those interested 

 in inheritance suggest are transmitted by the male as well as 

 by the female, and therefore through the intermediation 

 of the nucleus, are just these smaller individual, varietal, 

 specific and generic characters. The larger characters have 

 always been tacitly omitted from consideration, for the simple 

 reason that the investigation of them could only become 

 possible by the discovery of some means of bringing about 

 heterogeneous fertilization. 



Into the evidence, based on common experience and scientific 

 experiment, for the transmission of characters of some sort 

 by the male parent, and therefore by the nucleus, it is quite 

 unnecessary to go at length ; but the hybrids between various 

 genera of Sea-urchins have been such classical objects for 

 investigations of this kind, ever since the days of Boveri's 

 supposed production of a dwarf larva with the characters of 



H2 



