624 
THE VOYAGE OF H.M.S. CHALLENGER. 
The question naturally arises, whether or no Candeina is essentially a free-swimruing 
type in the same sense as Globigerina or Hastigerina ; and except on the hypothesis that 
an organism which is sometimes pelagic is necessarily always pelagic, for which there is no 
reasonable ground, the evidence is not sufficient to supply a positive answer. Hastigerina, 
the genus to which Candeina bears most resemblance in the extreme tenuity of the 
shell- wall, is comparatively common in surface gatherings, whilst its shells are very rare 
in the bottom ooze of the same areas, and are invariably much broken ; and it is difficult 
to see why there should be any discrepancy in the proportionate numbers of surface and 
bottom specimens if the life conditions are identical. On the other hand, it is worth 
mentioning that Candeina nitida sometimes occurs in dredged material which is almost 
entirely composed of organisms of pelagic habit. 
There is no record of the occurrence of the species in the fossil state. 
Family IX. RQTALIDXE. 
The Foraminifera of the Family Rotalidaj form a complicated and difficult group, 
assuming characters so diverse in their extreme modifications, that there is scarcely a 
single feature, beyond the calcareous shell and its hyaline and perforate texture, that is 
common to the whole of the members. There are nevertheless certain peculiarities of 
structure and modes of growth that may be regarded as distinctively “ Rotaline ” ; and, 
though these are not common to the entire series, the exceptional cases are comparatively 
few, and the connection of the aberrant forms with those of more typical character is 
for the most part sufficiently obvious. Thus, with the rare exceptions alluded to, the 
test is always polythalamous, and in its early stages, if not throughout, the chambers are 
spirally arranged ; and, typically, the spire is inequilateral, that is to say, the convolu- 
tions are more embracing on one side than the other. It is needless at the outset to 
dwell upon these and other characters of more or less general application, which will be 
best understood and their comparative significance best determined when considered with 
relation to the consecutive generic types. 
The simplest of all spiral and perforate Foraminifera are comprised in the genus 
Spirillina, the test of which consists typically of an undivided tube coiled regularly 
upon itself. Usually the spire is symmetrical and complanate ; but in some cases the 
coils are more or less oblique, foreshadowing the inequilateral construction of the true 
Rotalince, and in others the successive convolutions are superimposed more or less 
vertically, so as to produce a conical test. The conical Spirillince are scarcely distin- 
guishable from the feebler varieties of Patellina ; and the relationship of the genus to 
the Rotaline group is further evidenced by the tendency of the weaker modifications of 
Pulvinulina to assume Spirilline characters. 
