CONCLTJDINa SUMMAET DEEIVATION OF EXISTING EEOM ANCIENT POEMS. 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 difierentiations, 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 Faces 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 
Eheenbekg in regard to a considerable number of Cretaceous forms ; since fully con- 
finned and extended as regards the Tertiary fauna by the admirable researches of 
Messrs. Fupert Jones and Parker on the Ehizopodal Fauna of the Mediterranean, as 
well as by my own comparison of the recent and fossil types of OrhitoUtes, Orhiculina, 
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- 
