326 
THE VOYAGE OE H.M.S. CHALLENGER. 
Lituolidce. Under ordinary circumstances, there is no difficulty in distinguishing the 
H or mo since from their larger Lituoline isomorphs, by their thin walls and smooth, almost 
homogeneous, tests, and amongst the smaller species by their regularity and symmetry of 
form. 
In point of distribution Hormosina is essentially a deep-water type. Except 
possibly in the Jurassic formation of Switzerland (Haeusler), no representative of the 
genus has been found in the fossil state. 
Hormosina globulifera, H. B. Brady (PI. XXXIX. figs. 1-6). 
Hormosina globulifera, Brady, 1879, Quart. Journ. Micr. Sci., vol. xix., N. S., p. 60, pi. iv. 
figs. 4, 5. 
„ „ Carpenter, 1881, The Microscope, 6th ed., p. 561, fig. c. 
Test composed of a single spherical chamber with a tubulated orifice, or of several (2 
to 6) such chambers, each larger than its predecessor, and more or less embracing it. 
Segments arranged in straight or curved linear series, and terminating in a narrow 
tubular neck, which serves as the general aperture. Walls thin, texture very finely 
arenaceous, surface smooth. Length of polythalamous specimens, |-th inch (3 mm.) or less. 
Adult specimens of Hormosina globulifera have chambers varying in number from 
one to five or six, and the species affords frequent examples of the tendency, not 
uncommon amongst the Foraminifera, to cease growing after the production of a segment 
of relatively large size. As a rule, the specimens which have the greatest number of 
segments are those with the smallest initial chambers ; and, on the other hand, if a very 
large primordial chamber is formed, the test usually remains monothalamous, and do 
further growth takes place. This is well illustrated by a comparison of the Lageniform 
specimen (PL XXXIX. fig. 1), with the earlier segments of figs. 3 and 4 ; and it will be 
further observed how nearly the dimensions of the arrested monothalamous test approach 
those of the final segments of figs. 2, 3, and 4 respectively. In the somewhat anomalous 
specimen (fig. 5) a second large chamber has been formed before growth has ceased. 
The same rule which applies to the first chamber in the present species holds good 
also, more or less, during the later stages of growth amongst Foraminifera generally ; and 
it may often be noticed, in calcareous as well as arenaceous species, that with the formation 
of a chamber of abnormal size, the growth, that is to say, the continued production of 
sarcode-segments, comes to an abrupt termination. But whatever may be the significance 
of monothalamous as distinct from polythalamous tests amongst the Bhizopoda of other 
groups, the character in the present case is not even of varietal importance. 
The only species with which Hormosina globulifera is likely to be confounded is 
Reophax pilulifera, and from this it may generally be distinguished by its thinner walls 
and finer texture, and by its smooth and neatly finished exterior. 
