OBSERVATIONS ON LIVING SPECIMENS. ll 
DEVELOPMENTAL STAGES. 
Too little attention has been paid to the study of the develop- 
mental stages in the Foraminifera. It has been denied by many 
authors that such stages as are seen in the tests of many of the 
multilocular Foraminifera have any significance. If, however, the 
developmental stages are studied and compared with what is known 
of the development of the particular group in the fossil series, a 
close relation will be found. This comparison is somewhat compli- 
cated by the lack of certain stages in the asexual or megalospheric 
forms. In the microspheric or sexual form, where the stages are most 
nearly complete, the comparison leads to a very close relationship 
between the ontogeny and the phylogenetic history of the group. 
It seems fair to say that if a careful study is made along these 
lines, a very complete classification can be developed in many of 
the families which will rest upon better ground than the present 
classification. 
The Tortugas collection shows many interesting problems in devel- 
opmental stages, but they will be considered in this paper only in an 
incidental way. 
VARIATION. 
Much of the so-called variation in the Foraminifera may be 
divided into groups. The first of these may be the differences due 
to the different stages in development and which are no more to be 
classed as variation than the differences in such molluscan shells as 
Cyprea, when the young is a coiled spire and the adult a greatly 
expanded chamber covering the whole early stages. 
The second of these are the differences due to the two distinct 
forms, asexual and sexual, or megalospheric and microspheric. These 
differences should be taken into consideration in eliminating so-called 
variation. Differences due to these causes should strictly no more 
be classed as variations than the differences in sexual characters 
among the higher animals. The third group of characters show 
true variations. That is, actual size in adults, variations in orna- 
mentation in adults (not in comparison of young and adult tests), 
and other like characters. When such characters alone are taken 
it will, I am very sure, be found that the actual amount of true 
variation in this group is relatively small. 
An additional cause for much of the so-called variation is probably 
the failure of many authors to carefully divide species. A study of 
the Foraminifera from an area such as that of the western Atlantic 
from Newfoundland to the coast of Brazil shows that many faunas in 
the region have very definite limits, bathymetrically and geo- 
graphically. Some species are very restricted in their distribution 
and others more widespread, exactly as in other groups of the animal 
