258 THE ZOOLOGIST. 



in order to reconcile these apparent contradictions (Mendelian 

 and Darwinian), recognize that we are arguing about two entirely 

 different matters, namely (a) the germ plasm evolution ; and 

 (b) the ornamental accompaniments of that evolution — the 

 colour, hair, &c, of Mendelian investigators. 



We must cast aside all endeavour to attach to such super- 

 ficialities the index of true species (extreme). If we recognize 

 the essential evolution as that of essence and germ, the difficulty 

 of conflicting theories fades into insignificance. 



Mendelians appear to suggest (or this is how I understand 

 it) that the Horse and Ass contracting germs should contain 

 certain factors in their Mules, some to account for the Horse 

 points, and some for the Ass points. The inference from this is 

 that otherwise they are to be held inalienable. To limit our 

 view to the differences of factors alone appears to me to obscure 

 the issue. The two combining entities must be considered as of 

 quite divergent composition. 



If we disregard this search for problematical factors, we can 

 regard the cells (in all intermediate crosses) as exactly what 

 they very probably are, namely, a composition of equal properties 

 of both parents, entities of mingled physiological combination, 

 and therefore of intermediate aspect. There is a hybrid Zebra- 

 Ass at Regent's Park, and if this animal proves fertile, I cannot 

 imagine that she would throw (to a mate of similar breeding) an 

 Ass, a Zebra, and two impure somethings. Why should she? 

 The answer appears obvious. 



Let us assume that there be factors (bio-chemical), as may 

 indeed be the case — there appears no reason why they should of 

 necessity be segregating ones. If such a result is to be proved 

 in all sperms, with no inherent specific diversity, there should 

 apparently be no limit to any monstrous hybrid of any parent- 

 age, or how would sterility be accounted for ? Chemistry of the 

 organisms has unknown possibilities ; it would appear hardly 

 capable, however, of turning an animal whose organism is half 

 Zebra into a homogeneous Ass. 



Segregating characters are of necessity more incompre- 

 hensible than intermediate ones ; there seems no need, therefore, 

 for any assumption that the latter must be conformable to the 

 same biological laws. The "presence and absence" theory 



