196 ORIGINAL ARTICLES. 



have made it clear that such a scheme will be most likely to approach 

 the truth, when its basis is laid in a thorough knowledge of the nature 

 and extent of those variations which every chief modification of this 

 type shows itself so peculiarly disposed to exhibit, and when in building 

 it up the idea of natural affinity is accepted as expressing not only degree 

 of mutual conformity, but actual relationship arising from community of 

 descent more or less remote. For the endless gradational departures 

 from any types which we may assume as fixed, and the occurrence of 

 links of connexion between such as present the best marked differenti- 

 ations, seem to me to point unmistakeably to this as the only escape from 

 that difficulty of indefinite multiplication, which attends the application 

 of the doctrine of distinct specific creations to a group in which scarcely 

 any two individuals are alike. 



The present aspect of this inquiry, in fact, may be not inappro- 

 priately compared with that of the oft-debated question as to the Races 

 of Mankind. In the one case, as in the other, the direct evidence of 

 descent affords cogent evidence as to the possible extent of modification 

 within the limits of particular races ; and when that evidence is brought 

 into relation with analogous facts in regard to the yet greater variations 

 of which we have direct evidence in the case of domesticated animals, it 

 points to conclusions of higher generality, which physiologists find no 

 difficulty in accepting. Now the modifications which any single type 

 of Foraminifera must have undergone, to give origin to the whole series 

 of diversified forms now presented by that group, are not greater in 

 comparison with the modifications of which we have direct evidence, than 

 are those which the advocate for the specific unity of the human races 

 has no hesitation in assuming as the probable account of their present 

 divergence. 



This view of the case derives great force from the fact that there is 

 strong reason to regard a large proportion of the existing Foraminifera 

 as the direct lineal descendants of those of very ancient geological pe- 

 riods — a doctrine first advanced by Professor Ehrenberg in regard to a 

 considerable number of Cretaceous forms, and since fully confirmed and 

 extended as regards the Tertiary fauna by the admirable researches of 

 Messrs. Rupert Jones and Parker, as well as by my own comparison 

 of the recent and fossil types of Orbitolites, Orhiculina, Aheolina, Oper- 

 culina, and Calcarina; and shown to be applicable also to the Secondary 

 fauna, as far back as the Triassic system, by the remarkable results of 

 the investigations of the same gentlemen in regard to a well-preserved 

 sample of it. Following out, by laborious and extended comparison, 

 the method of inquiry I have so much insisted on, thej r have found am- 

 ple evidence that a like range has prevailed through the whole succes- 

 sion of geological periods to which their researches have extended. 

 "Our own experience of the wide limits within which any specific group 

 of the Foraminifera multiply their varietal forms, related by some pe- 

 culiar conditions of growth and ornamentation, has led us to concur 

 fully with those who regard nearly every species of Foraminifera as ca- 

 pable of adapting itself, with endless modifications of form and structure, 



