taken as proved that all the materials of such deposits, with the exception, of course, of the remains of animals which we now know to live at the bottom of all depths, which occur in the deposit as foreign bodies, are derived from the surface.
"Mr. Murray has combined with a careful examination of the soundings a constant use of the tow-net, usually at the surface, but also at depths of from 10 to 100 fathoms, and he finds the closest relation to exist between the surface fauna of any particular locality and the deposit which is taking place at the bottom. In all seas, from the equator to the polar ice, the tow-net contains Globigerinæ. They are more abundant and of a larger size in warmer seas; several varieties, attaining a large size, and presenting marked varietal characters, are found in the intertropical area of the Atlantic. In the latitude of Kerguelen they are less numerous and smaller, while farther south they are still more dwarfed, and only one variety, the typical Globigerina bulloides, is represented. The living Globigerinæ from the tow-net are singularly different in appearance from the dead shells we find at the bottom. The shell is clear and transparent, and each of the pores which penetrate it is surrounded by a raised crest, the crest round adjacent pores coalescing into a roughly hexagonal network, so that the pores appear to lie at the bottom of an hexagonal pit. At each angle of this hexagon the crest gives off a delicate, flexible, calcareous spine, which is sometimes four or five times the diameter of the shell in length. The spines radiate symmetrically from the direction of the centre of each chamber of the shell, and the sheaves of long transparent needles crossing one another in different directions have a very beautiful effect. The smaller inner chambers of the shell are entirely filled with an orange-yellow granular sarcode; and the large terminal chamber usually contains only a small irregular mass, or two or three small masses run together, of the same yellow sarcode stuck against one side, the remainder of the chamber being empty. No definite arrangement and no approach to structure was observed in the sarcode, and no differentiation, with the exception of round bright-yellow oil-globules, very much like those found in some of the radiolarians which are scattered, apparently irregularly, in the sarcode. We never have been able to detect, in any of the large number of Globigerinæ which we have examined, the least trace of pseudopodia, or any extension, in any form, of the sarcode beyond the shell. . . .
"In specimens taken with the tow-net the spines are very usually absent; but that is probably on account of their extreme tenuity; they are broken off by the slightest touch. In fresh examples from the surface, the dots indicating the origin of the lost spines may almost always be made out with a high power. There are never spines on the Globigerinæ from the bottom, even in the shallowest water."There can now be no doubt, therefore, that the Globigerinæ live at the top of the sea; but the question may still be raised whether they do not also live at the bottom. In favor of this view, it has been urged that the shells of the Globigerinæ of the surface never possess such thick walls as those which are found at the bottom, but I confess that I doubt the accuracy of this statement. Again, the occurrence of minute Globigerinæ in all stages of development, at the greatest depths, is brought forward as evidence that they live in situ. But, considering the extent to which the surface-organisms are devoured, without discrimination of young and old, by Salpæ and the like, it is not wonderful that the shells of all ages should be among the rejecta-
