CONCLUDING STJMMAEY : DEEIVATION OF EXISTING FEOM ANCIENT FOEMS. 581 



256. The same general doctrine having thus been shown to hold good in regard to 

 all the chief natural subdivisions of the Foraminiferous group, it is not my purpose at 

 present to prolong the inquiry in this direction. The systematic study of this tribe 

 needs to be prosecuted far more extensively than my own time and opportunities have 

 admitted, to enable even an outline-scheme to be framed, which should represent an 

 approximation to the true relations of its principal families. But I think I have made 

 it clear that such a scheme will be most likely to approach the truth, when the basis of 

 it 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 occurrence of endless gradational departures from any 

 types which we may assume as fixed, and of links of connexion between such as present 

 the best-marked differentiations, seem to me to point unmistakeably to this as the only 

 means of escape from that difficulty of indefinite multiplication which attends the doc- 

 trine of distinct specific creations when applied to a group in which scarcely any two 

 individuals are alike. The case, in fact, is very analogous to that of the relationship 

 between the various members of the family of Mankind; for whilst the historical 

 evidence of actual change in them is so incomplete as well as so limited in its range, as 

 to be quite inadequate of itself to establish their community of descent, yet when that 

 evidence is considered in its relations to analogous facts drawn from the far greater 

 variations of domesticated animals, and to the manifold gradations by which the 

 extreme types are connected, physiologists of the highest eminence have felt themselves 

 justified in accepting that community as probable. Now the modifications which any 

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

 diversified forms presented by that group, are not greater in comparison with those 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. 



257. 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 descend- 

 ants of those of very ancient geological periods ; a doctrine first advanced by Professor 

 EHRENBERG in regard to a considerable number of Cretaceous forms ; since fully con- 

 firmed and extended as regards the Tertiary fauna by the admirable researches of 

 Messrs. RUPERT JONES and PARKER on the Rhizopodal Fauna of the Mediterranean, as 

 well as by my own comparison of the recent and fossil types of Orlitolites, Orliculina, 

 Alveolina, Operculina, and Calcarina; and shown to be applicable also to the Secondary 

 fauna, as far back as the upper part of 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, they have found ample evidence that the fact of a wide range of varia- 



