HARDWICKE'S SCIENCE-GOSSIP. 



31 



found within Orbulina, that the latter is simply a 

 special reproductive chamber budded from the 

 former, and capable of existing independently. I 

 am rather inclined to the latter view, although I 

 think much careful observation is still required to 

 substantiate it ; and some even of our own observa- 

 tions would seem to tell somewhat in the opposite 

 direction. Although Orbulina and Globigerina are 

 very usually associated, in different localities, they 

 are so in different proportions ; 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, Orbulina 

 is most fully developed and most abundant in the 

 warmer seas. 



Associated with these forms, and, like them, living 

 on the surface and dead, and with their shells in 

 various stages of decay at the bottom, there are two 

 very marked species or varieties of Pulvinulina, P. 

 Menardii, and P. micheliniana. The general struc- 

 ture 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 usually 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 chambers are closely and minutely 

 perforated. The external surface of the wall is 

 nearly smooth, and no trace of a spine has ever been 

 detected. Pulvinulina Menardii has a large dis- 

 coidal depressed shell, in diameter consisting of 

 a series of flat chambers overlapping one another, 

 like a number of coins laid down somewhat irre- 

 gularly, but generally in a spiral : each chamber is 

 bordered by a distinct somewhat thickened solid rim 

 of definite width. On the lower surface of the shell 

 the intervals between the chambers are indicated 

 by deep grooves. The large irregular opening of 

 the final chamber is protected by a crescentic lip, 

 which in some specimens bears a fringe of spine- 

 like papillae. This form is almost confined to the 

 warmer seas. It is very abundant on the surface, 

 and still more so during the day, at a depth of ten 

 to twenty fathoms in the Mid- Atlantic ; and it 

 enters into the composition of the very characteristic 

 Globigerina ooze of the "Dolphin Pise " in almost 

 as large proportions as Globigerina. Pulvinulina 

 micheliniana is a smaller variety ; the upper surface 

 of the shell is flattened as in P. Menardii, but the 

 chambers are conical and prolonged downwards, so 

 that the shell is deeper and somewhat turbinate. 

 The two species usually occur together; but P. 

 micheliniana has apparently a much wider distribu- 

 tion than P. Menardii, in which the former was 

 limited to the region of the trade-winds and the 

 equatorial drift-current, and was found rarely, if at 

 all, to the south of the Agulhas current ; the latter 



accompanied us southward as far as Kerguelen 

 Land. Both forms of Pulvinulina, however, are more 

 restricted than Globigerina, for even P. micheliniana 

 became scarce after leaving the Cape, and the 

 wonderfully pure calcareous formation in the neigh- 

 bourhood of Prince Edward Island and the Crozets 

 consists almost solely of Globigerina bulloides ; and 

 neither species of Pulvinulina occurred to the south 

 of Kerguelen Land. 



Over a very large part of the "Globigerina-ooze" 

 area, and especially in those intertropical regions in 

 which the formation is most characteristically deve- 

 loped, although the great bulk of the ooze is made 

 up of entire shells and fragments of shells of the 

 above-described foraminifera, besides these there is 

 frequently a considerable proportion (amounting in 

 some cases to about twenty per cent.) of fine granu- 

 lar matter, which fills the shells and the inter- 

 stices between them, and forms a kind of matrix or 

 cement. This granular substance is, like the shells, 

 calcareous, disappearing in weak acid to a small 

 insoluble residue : with a low microscopic power it 

 appears amorphous, and it is likely to be regarded 

 at first sight as a paste made up of the ultimate 

 calcareous particles of the disintegrated shells, but 

 under a higher power it is found to consist almost 

 entirely of " coccoliths" and "rhabdoliths." I need 

 scarcely enter here into a detailed description of 

 these singular bodies, which have already been 

 carefully studied by Huxley, Sorby, Giimbel, Carter, 

 Oscar Schmidt, Wallich, and others. I need only 

 state that I believe our observations have placed it 

 beyond a doubt that the "coccoliths" are the sepa- 

 rated elements of a peculiar calcareous armature 

 which covers certain spherical bodies (the " cocco- 

 spheres " of Dr. Wallich). The rhabdoliths are the 

 like elements of the armature of extremely beauti- 

 ful little bodies, which have been first observed by 

 Mr. Murray, and naturally called by him " rhabdo- 

 spheres." Coccospheres and rhabdospheres live 

 abundantly on the surface, especially in warmer 

 seas. If a bucket of water be allowed to stand over 

 night with a few pieces of thread in it, on examining 

 the threads carefully many examples may usually be 

 found attached to them ; but Mr. Murray has found 

 an unfading supply of all forms in the stomachs of 

 Salpse. 



What these coccospheres and rhabdospheres are 

 we are not yet in a position to say with certainty ; 

 but our strong impression is that they are either 

 alga? of a peculiar form, or the reproductive gem- 

 mules, or the sporangia of some minute organism, 

 probably an alga, in which latter case the coccoliths 

 and rhabdoliths might be regarded as representing 

 in position and function the " amphidisci " on the 

 surface of ]the gemmules of Spongilla, or the spiny 

 facets on the zygospores of many of the Desmideae. 

 There are many forms of coccoliths and rhabdoliths, 

 and many of these are so distinct that they evidently 



