96 



NATURE 



[Dec. 3, 1874 



less degi'ee spiny when the shell has attained its full develop- 

 ment. 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 witli a high 

 power. There are never spines on the Globigerina; from the 

 bottom, even in the shallowest water. Two or three very marked 

 varieties of Globigerina occur ; but I certainly do not think that 

 the characters of any of them can be regarded as of specific 

 value. 



There is still a good deal of obscurity about the nature of 

 Orbiilina uiiivc-rsa, an organism which occurs in some places in 

 large proportion in the Globigerina ooze. Tlie shell of Orbulina 

 is spherical, usually about '5 millimetre in diameter, but it is 

 found of all smaller sizes. The te.xture of the mature shell 

 resembles closely that of Globigerina, but it differs in some 

 important particulars. The pores are markedly of two ditferent 

 sizes, the larger about four times the area of the smaller. The 

 larger pores are the less numerous ; they are scattered over the 

 surface of the shell without any appearance of regularity ; the 

 smaller pores occupy the spaces between the larger. The crests 

 between the pores are much less regular in Orbulina than they 

 are in Globigerina ; and the spines, which are of great length 

 and extreme tenuity, seem rather to arise abruptly from the top 

 of scattered papil!ce than to mark the intersections of the crest. 

 This origin of the spines from the papillcc can be well seen with 

 a moderate power on the periphery of the sphere. The spines 

 are hollow and flexible ; they naturally radiate regularly Irom 

 the direction of the centre of the sphere ; but in specimens which 

 have been placed under the microscope with the greatest care 

 they are usually entangled together in twisted bundles. They 

 are so fragile that the weight of the shell itself, rolling about 

 with the motion of the ship, is usually sufficient to break off the 

 whole of the spines and leave the papillx' only projecting from 

 its surface in the course of a few minutes. In some examples, 

 either those in process of development, or a series showing a 

 varietal divergence from the ordinary type, the shell is very thin 

 and almost perfectly smooth, with neither papilUr? nor spines, nor 

 any visible structure, except the two classes of pores, which are 

 constant. 



The chamber of Orbulina is often almost empty ; even in 

 the case of examples from the surface, which appears from the 

 freshness and transparency of the shell to be living, it is never 

 full of sarcode ; but it frequen'ly contains a small quantity of 

 yellow sarcode stuck against one side, as in the last chamber of 

 Globigeriua. Sometimes, but by no nie.ans constantly, within 

 the chamber of Orbulina there is a little chain of three or four 

 .small chambers singularly resembling in form, in proportion, and 

 in sculpture, a small Globigerina ; and sometimes, but again by 

 no means constantly, spines are developed on the surface of the 

 calcareous walls of these inner chambers, like those on the test 

 of Globigerina. The spines radiate from the position of the 

 centre of the chambers and abut against the insides of the wall 

 of the Orbulina In a few cases the inner chambers have been 

 observed apparently arising within or among the sarcode adher- 

 ing to the wall of the Orbulina. 



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 as representing the smaller chamber 

 of Globigerina, and the outer wall as the equivalent of the large 

 outer chamber of Globigerina 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 t^ibulina, 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 

 observations would seem to tell somewhat in the opposite direc- 

 tion. Although Orbulina and Globigerina are very usually 

 associated, in different localities, they are so in different propor- 

 tions ; and in the icy sea to the south of Kerguelen, although 

 Globigerina was constantly taken in the surface-net, not a single 

 Orbuhna was detected. Like Globigerina, Orbulina is most 

 fully developed and most abundant m 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. mciiardii, and P. muhdiniaita. Tlie general 

 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 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. Piil- 

 2'iiiii/iiia niinai-dii has a large discoidal depressed shell, in 

 diameter consisting of a series of flat chambers overlapping one 

 another, like a number of coins laid down somewhat irregularly, 

 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 Globi- 

 gerina ooze of the " Dolphine Rise" in almost as large pro- 

 portions as Globigerina. Pitlviniilina niic]idiniaita is a smaller 

 variety ; the upper surface of the shell is llattened as in P. 

 vienardii, but the chambers are conical and prolonged down- 

 wards, so that the shell is deeper and somewhat turbinate. The 

 two species usually occur together ; but P. inkhehniana has 

 apparently a much wider distribution than P.mtnardh, 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 south- 

 ward as far as Kerguelen Land. Both forms of Pulvinulina, 

 however, are more restricted than Globigeiina, for even /'. 

 Diicheliniana became scarce after leaxing the Cape, and the 

 wonderfully pure calcareous formation in the neighbourhood 

 of Prince Edward Island and the Crozets consists almost solely 

 of Glohis^criua hulloidcs ; 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 developed, 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 granular matter, which fills the shells 

 and the interstices between them, and forms a kind of matrix 

 or cement. This granular substance is, like the shells, cal- 

 careous, 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 ulti-a 

 mate 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, GUmbel, Carter, Oscar 

 Schmidt, Wallich, and others. I need only strte that I believe 

 our observations have placed it beyond a doubt that the " cocco- 

 liths " are the separated elements of a peculiar c ilcareous 

 armature which covers certain spherical bodies (the " cocco- 

 spheres" of Dr. Wallich.) The rhabdoliths are the like ele- 

 ments of the armature of extremely beautiful little bodies, 

 which have been first observed by Mr. Murray, and naturally 

 called by him "rhabdospheres. Coccospheres and rhabdo- 

 spheres 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 thiead in it, on examining the threads carefully 

 many examples may usually be found attached to them ; but 

 Mr. Murray has found an unfailing supply of all forms in the 

 stomachs of Salpic. 



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 algai of a peculiar form, or the reproductive 

 gemmules, 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 " amphi- 

 disci " on the surface of the gemmules of Spongilla, or the sp. ny 

 facets on the zygospores of many of the DestnideK. There are 

 many forms of coccoliths and rhabdoliths, and many of these are 



