Bildung und Bedeutung der Artbegriffe bei den Foraminiferen. 



69 



kehrenden Wirkungen dieser vererblichen Gestaltungskräfte sind die reellen Grundlagen für die 

 Bildung von Artbegriffen auch bei den Foraminiferen, genau nach derselben Methode, nach welcher 

 in allen andern Thierklassen Artbegriffe abgeleitet werden. 



Der berühmte Foraminiferenforscher W. B. Carp enter und seine verdienten Mitarbeiter 

 W. K. Parker und T. Rupert Jones sind hierin anderer Meinung. Prof. Carpenter schreibt 

 in seinem grossen Werke: Introcluction to the study of the Foraminifera, London 1862, hierüber 

 Folgendes : 



p. X: „The ränge of Variation is so great among Foraminifera, as to include not merely 

 the differential characters which systematists proceeding upon the ordinary methods have 

 accounted specific, but also those upon which the greater part of the genera of tliis group 

 have been founded, and even in some instances those of its Orders." 



„The ordinary notion of species, as assemblages of individuals marked out from each 

 other by definite characters that have been genetically transmitted from original prototypes 

 similarly distinguished , is quite inapplicable to this group; since even if the limits of such 

 assemblages were extended so as to include what would eise where be accounted genera, they 

 would still be found so intimately connected by gradational links, that definite lines of demarcation 

 could not be drawn between them." 



„The only natural Classification of the vast aggregate of diversified forms which this 

 group contains. will be one which ranges them according to their direction and degree of diver- 

 gence from a small number of principal family-types ; and any subordinate groupings of genera 

 and species which may be regarded merely as assemblages of forms characterised by the nature 

 and degree of the modifications of the original type, which they may have respectively acquired 

 in the course of genetic descent from a common ancestry." 



„Even in regard to these family-types, it may fairly be questioned whether analogical 

 evidence does not rather favour the idea of their derivation from a common original, than that 

 of their primitive distinctness." 



Und ferner p. 56: 



„All that as seems to us at present feasible to attempt, is to group them around certain 

 generic types, each marked by some combination of characters which impresses on it (to speak) 

 a distinctive physiognomy, and to trace out the principal modifications to which these types are 

 subject through the separate or combined Variation of their characters. Among these modifications 

 there will generally be found some which indicate an affinity towards other types, so as to 

 diminish the intervals between each type and those to which it is related. Wherever such gra- 

 dation can be shown to exist with anything like complete continuity, its presence will be accounted 

 a sufficient reason for including the whole series (however diversified in its extreme forms) under 

 one and the same generic designation; where, again, it seems likely to be established by further 

 research (which is sometimes especially the case in regard to extinct types) the modification thus 

 related will be ranked as a sub-genus." 



„The impracticability of applying the ordinary method of definition to the genera of 

 Foraminifera becomes an absolute impossibility in regard to species. For whether or not there 

 really exist in this group generic assemblages capable of being strictly limited by well marked 

 boundaries, it may be affirmed with certainty that among the forms of which such assemblages 



