determined, for examination, to sacrifice two or three more of the few specimens I still possess, of Operculina Arabica containing the living animal when they were brought up with the "sounding-lead" on the south-east coast of Arabia in 1844, now of course dry; and for this purpose one of these was placed in very weak spirit-and-water for a night first, another examined at the moment of being broken-up in water, and a third subjected to a very weak solution of nitric acid and water for a night, with the following results. It was found that in the latter experiment, the chambers and the canals, after having been gradually deprived of their calcareous matter, still retained their form in a membranous state, and under this condition they will now be described. Chamber. The horizontal or exposed walls of the chamber in a membranous state present a number of semi-opaque circular bodies arranged in a pavement-like form close together, each of which has at depression or hole in the centre, and these correspond to the "vertical tubuli;" while the septal borders are composed of a transparent membrane without these bodies, but pierced here and there with large holes from which tubes are extended to the interseptal canals. The marginal border of the chamber is also supplied by a transparent membrane loosely attached to the spicular cord, but the base or internal margin is firmly fixed to the marginal plexus of canals; now of course in the way we are examining them all rendered membranous by the absence of the calcareous matter.

The chamber thus reduced to a membranous state is found to contain in its cavity various bodies, viz. small and large spherules, and starch-grains, to which we will now severally direct our attention.

Small Spherule.-This consists of a spherical portion of semi-opaque, homogeneous matter, surrounded by a delicate, spherical, transparent cell 1-5400th of an inch in diameter. The chamber may contain a few only, or be crammed with these bodies, and they are observed to be massively attached to branched stems or filaments like bunches of grapes.

Large Spherule.-The large spherule consists of a spherical portion of homogeneous matter charged with granules and enclosed in a spherical, transparent capsule about 1-1800th of an inch in diameter. The capsule is not always visible if present, and the form frequently slightly elliptical, while the colour is sometimes yellowish by transmitted light like that of dried albumen, and at others white by reflected light, as if there were calcareous matter in it; perhaps the former difference may be from drying or pressure, while the latter is evidently that of advancement in development.

Starch-grains.-These are thin, flat, and variable in size, but otherwise bear the unmistakeable characters of the "starch-grain." They were not numerous but always present, and, with many portions of the other soft substance of the cavity of the chamber, became purple and blue respectively, under the influence of the deliquescent, yellowish liquor of iodide of potassium assisted by a little sulphuric acid.

Canal-system. The canals having been deprived of their calcareous matter became equally membranous with the chamber, and those portions forming a communication between the chamber and the "interseptal canals" freely admitted the largest spherules to pass through them from the former to the latter; besides this, I find a number of them in one of my dried specimens without the animal, in all parts of the canal-system.

From these facts we learn that there are two kinds of spherules produced in the chambers, the larger of which appear to be but an advanced state of the smaller, but whether this be the correct view, or that the smaller ones be the sperm-cells or some other organ belonging to the chamber, remains to be shown. That the large spherules cannot be viewed in any other light than as propagative bodies, there can be no doubt now; but whether again, these be impregnated or unimpreg nated reproductive agents also remains to be shown. That they are the same which I have already pointed out as the reproductive agents in both the Euglypha and in Amœba verrucosa (loc. cit.) appears also to me to be undoubted,

The next fact is, that the passage of these bodies freely from the chamber into the interseptal canals proves that, one use at least of the canals is, as before stated, to give exit to the contents of the chambers.

Lastly, the presence of starch-grains, although not wonderful as the organism is distinctly a Rhizopod and starch-grains abound in Spongilla, especially in the capsules, is nevertheless interesting, as their presence also in the winter-eggs of the freshwater Polyzoa and the close resemblance of this "egg" to the capsule of Spongilla, thus makes the presence of starch-grains in all, one point at least, which so far, allies these organisms. Not only this, but the resemblance of the canal-system, or rather the sarcodal filaments which it contains, to the mycelium of Fungi as before noticed, and the evident connexion that also exists between Spongilla and some of the parasitic developments of the cell-contents of the Algae (now properly regarded by Pringsheim as allied to Achlya and Saprolegnia), whose spores first consisting of monociliated polymorphic cells then lose their cilium and become

simple rhizopods, while other developments of this kind are distinct Fungi putting forth sporangia with defined sporules, - seems to point out the passage of the animal into the fungal kingdom through the Foraminifera and Sponges. The parasite to which I more particularly allude is that termed by Pringsheim, Pythium entophytum, which grows out from the cell-contents of Spirogyra, and in its sporangia produces the monociliated spores mentioned, which, in 1857, I described as furnishing an instance of the "transformation of the vegetable protoplasm into Actinophrys," forsaking my original argument that these products must be parasitical, which Pringsheim's discoveries have now confirmed.+

Besides the course which the spherules have for their exit through the canal-system, some of my recent specimens present a hole here and there at the base of the few last chambers, opposite the great spiral canal, in which holes the large spherules, now white, may be seen, as if in the act of being voided, and probably from the great spiral canal. A single large hole with smooth margin evidently formed by the animal itself also appears here and there sometimes, in the side of the chambers, and this may have been for the purpose of giving exit to young Operculina, which had become too large to obtain their issue in the ordinary way, such as those noticed by Professor Schultze in the Rotalida ("Annals," vol. vii, p. 306.-1861), and Dr. S. Wright (id. p. 357, vol. vii,). But both these kinds of holes must be regarded as accidental, and not as regular developments of the test.

NUMMULITES.

The structure of the test of Nummulites is precisely that of Operculina, plus the lateral or vertical growth of the former, which is but a repetition, in plan, of the horizontal plane. Of this I was aware in 1852, when my description of the structure of Operculina was published, and my diagram of an infiltrated specimen of N. Acuta (Ann. l. c.), to confirm this, accompanied it. Since then, as before stated, the "canal-system" has been figured by Ehrenberg from an infiltrated specimen of N. striata; and within the last twelve months I have been able to see everything which I have described in the test of Operculina exemplified in richly infiltrated specimens of another of the "Striatæ," viz. N. Ramondi, accompanied by equally richly infiltrated specimens of Operculina, so that the means of identification has through the latter been most satisfactory.

*"Annals," vol. xix, pl. 259.

Ann. des Sc. Nat. t. xi, pl. 349, pl. 7, Bot.-1859.

Canal-system. The lateral or vertical development of Nummulites being the only additional part to the horizontal plane as it exists in Operculina, I have merely to state of the canal-system of this, that radiating branches are continued upward towards the centre or umbilicus of the nummulite from the great "spiral" canals of the cord, or from others near this, along each interseptal space, and from each turn of the cord; that vertical branches also from each turn of the cord opposite the interseptal spaces respectively keep up a communication by joining the radiating branches of the different layers of the spiral lamina, between the marginal plexures of the turns of the cord respectively and the surfaces; and that, in some nummulites, where there is a corresponding division in the portions of the chambers extending up towards the centre, with the turns of the spire, the radiating branches are connected by transverse ones; so that, in fact, each chamber is surrounded by an anastomosing circle of canals thus formed. While, in the reticulated nummulites, this anastomosis becomes retiform from the reticulated division of that part of the chambers which enters into the composition of the spiral lamina. Lastly, this canal-system sends off branches which open on the surface in the course of the interseptal spaces and along the spiral canals as in Operculina. Thus in each lamina of the nummulite the canal-system of the horizontal plane is repeated.

Vertical tubuli.-These enter into the formation of each spiral lamina just as they do into the single one of Operculina.

Non-tubular spaces.-Such are parts of the test which are not traversed by either the vertical tubes or the branches of the canalsystem, and, as before stated, in recent Operculina are marked by a homogeneous, semi-transparency of the shell-substance, while in the fossilized species they are opaque and white; a transition which leads to the knowledge of what they are and were in Nummulites. They may be linear, as when forming that part of the test over the interseptal spaces, or punctiform as when in the midst of the vertical tubuli, and in both positions afford signs, according to their form and number, for specific distinction. In N. Biaritzensis these white parts may be seen to form also a minute branch-work, which extends perpendicularly outwards from the septal lines; and in N. perforata, a similar branch-work may be observed to spread from both the septal lines and the puncta (very like the lacunæ and their branch-work in bone), but to such an extent in some specimens as to present a minute reticulation all over the cameral spaces, so much resembling a capillary canal structure that, at first sight, there seems to be no doubt of it. However,

their being formed of an opaque white substance like the septal lines and the puncta, first leads to the opinion that they are not tubes; and this is confirmed by microscopical examination of portions of the spiral lamina of N. perforata presenting this structure, when ground down to a thinness sufficient to allow the light to pass through them; for besides the absence of any double line indicative of the presence of a tube in these white lines which then are found to be made up of little disjoined portions of opaque material, a lash of branches from the "canal-system may here and there be observed to come through one of the puncta, and spread out among these white lines, when the double line and transparency indicative of a continued canal in them, at once and by contrast, shows the nature of both. Thus from what has been stated we see that, neither the white puncta nor the minute white branch-work of lines were ever tubular. In most nummulites the white puncta appear on the surface, and, when examined by a vertical section of the nummulite, are observed to be more or less conical, and of different lengths, according with the date of the commencement of their development; those which began with the earliest parts of the nummulite being longest. They arise in points from the surface of the chambers and the interseptal spaces, and end at the periphery, on a level with the rest of the test, but, being harder than the latter, they project on weathering, become rounded, and thus give the fossil a more or less granular surface. Now, in none of these white lines, white puncta, nor minute white branch-work, have I ever been able to see any indication, either in the recent Operculina, the fossilized infiltrated one, or in Nummulites, any branches of the canal-system, except by accident. Neither in the ends of the columns in Orbitoides dispansa, which are the same as those of nummulites, have I, in the most richly and minutely infiltrated specimens, been able to see in the ends of the white columns on the surface any red or yellow point indicating that they are always in connexion with a branch of the canal-system which traverses them longitudinally. So we must set these portions down as having nothing to do with the canal-system, however much they may conduce to the strength of the test.

Thus we see that the " très-petits canaux " of MM. d'Archiac and Haime (p. 60) were the "vertical tubuli; "their" canaux moyens,' the openings of the canal-system on the surface and along the spiral canals and spicular cord; and their "larges canaux," no canals at all, but the ends of the columns of condensed shell-substance. Dr. Carpenter, who also at first considered the latter canals, renounced this view long ago, (Phil. Trans. 1856, p. 553, foot-note).