CHAP. 11.] TENERIFFE TO SOMBRERO. 207 
Major Owen regards Orbulina as a distinct organism, nearly 
allied to Globigerina, but differing so far from it as to justify 
its separation into a special subgenus. He considers the small 
inner chamber of Orbulina to represent the smaller chamber of 
Globigerina, and the outer wall as the equivalent of the large 
outer chamber of Globigerima, developed in this form as an in- 
vesting chamber. Count Pourtales, Max Schultze, and Krohn, 
on the other hand, believe—on account of the close resemblance 
in structure between the two shells, their constant association, 
and the undoubted fact that an object closely resembling a 
young Globigerina is often found within Orbulina—that the 
latter is simply a special reproductive chamber budded from 
the former, and capable of existing independently. Iam rather 
inclined to the latter view, although I think much careful ob- 
servation is still required to substantiate it; and some even of 
our own observations would seem to tell somewhat in the op- 
posite direction. Although Orbulina and Globigerina are very 
usually associated, they are so in different proportions in differ- 
ent localities; and in the icy sea to the south of Kerguelen, 
although Globigerina was constantly taken in the surface-net, 
not a single Orbulina was detected. Like Globigerina, Orbu- 
lina is most fully developed and most abundant in the warmer 
seas. 
Associated with these forms, and, like them, living on the 
surface—and dead, with their shells in various stages of decay, 
at the bottom—there are two very marked species or varieties 
of Pulvinulina, P. Menardi and P. Micheliniana. The gen- 
eral structure of Pulvinulina resembles that of Globigerina. 
The shell consists of a congeries of from five to eight chambers, 
arranged in an irregular spiral. As in Globigerina, the last 
chamber is the largest; the inner smaller chambers are usual- 
ly filled with yellow sarcode; and, as in Globigerina, the last 
chamber is frequently nearly empty, a small irregular mass of 
sarcode only occupying a part of the cavity. The walls of the 
