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into two portions, each of these behaves precisely as another oil-globule does by instantaneously presenting an unbroken outline, that the said oil-globule is differently constituted at its surface and in its interior. The same argument applies, and with redoubled force, to a mass of albumen suspended in water; for here the tendency to assume a spherical form is by no means so pronounced as in an oil-globule; and if we break up the mass into a number of smaller masses, we have presented to us appearances which very closely resemble those observable in the pseudopodium of the Amoeban Rhizopod. Indeed so close is the resemblance, that, barring the element of vitality (which the chemist is still as far off as ever from producing at call), we have before our eyes those very "fundamental potentialities" which a highly imaginative rendering of certain appearances has declared to be typical of the living sarcode of the Rhizopod.

Were it not that it befits us to speak with bated breath of the mighty dead, another instructive argument on this subject might be adduced from the history of the rise and fall of the unfortunate "Bathybius."

But the fact is, that, divide the sarcode body of a living Amaban, or even an Actinophryan, Rhizopod as we may, by pressure or other agency, the divided surface will forthwith present every character presented by the undivided portion: any peculiarity of outline, if present in the undivided part, will at once reappear in the divided part; any seeming contrast between the external layer and the contained mass within will instantly show itself; and the character of the pseudopodial processes will be the same. This identity of character in the divided and undivided surfaces is absolutely instantaneous, there being nothing like a gradual transition from one condition to another, such as we should undoubtedly be able to see taking place were the ruptured surfaces in any respect dissimilar to the rest of the mass. This is the view I have always advocated, its unacceptable point being, I presume, that it is quite unconformable with Dr. Carpenter's published definitions of Rhizopod structure.

As it would be foreign to the immediate purpose of the present paper to enter into all the details of the subject, I must confine myself to stating that the inconstancy of the pseudopodial characters in Amoeba, which is of course quite incompatible with the assumed presence of an external layer of much more highly developed sarcode than that which it encloses, is conceded (but without the inevitable inference which must be associated with it) in the Introduction to the Study of the Foraminifera,' 1862 (p. 23), when Dr. Carpenter says

that "sometimes Amaba puts forth a few broad lobated expansions; sometimes these are more numerous, slender, and elongated, assuming a radial direction; and occasionally they are so greatly multiplied, radiate with such regularity, and taper so uniformly from base to apex, as strongly to resemble the pseudopodia of ACTINOPHRYS.'

This is undoubtedly true; and I therefore leave Dr. Carpenter to reconcile the fact with his classification and definitions of the orders, of which I now subjoin a summary, taken from his paper in the Natural-History Review' to which reference has already been made *.

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After saying that "any small separated portion of the sarcode body of the Rhizopoda will behave itself after the characteristic fashion of its type" (that of Arcella behaving like that of Amoeba, that of Polystomella, or any other of the Foraminifera, like those of Gromia), and adding that "this fact seems to him to afford an additional justification of the employment of the characters furnished by the pseudopodia as the basis of a systematic arrangement of the class," he informs us that the characters of the three orders into which he proposes to distribute its various forms may be concisely summed up as follows:

“I. RETICULARIA.-The body composed of homogeneous granular protoplasm, without any distinction into ectosarc and endosarc; neither nucleus nor contractile vesicle; pseudopodia composed of the same substance as the body, extending and multiplying themselves by minute ramification, and inosculating completely wherever they come into contact; a con

It may be well to bear in mind that the article in the 'Review' appeared in 1861 as an avant-courier to the 'Introduction to the Study of the Foraminifera,' which appeared just a year afterwards. The tabular classification of the Rhizopods is taken from page 17 of the latter work.

tinual circulation of granular particles throughout the viscid substance of the body and its extensions. This order consists of the Foraminifera and the Gromida.

"II. RADIOLARIA.-Incipient differentiation of the protoplasmic substance into endosarc and ectosarc, the former semifluid and granular, the latter more tenacious and pellucid; a nucleus and contractile vesicle; pseudopodia rod-like, tapering from base to point, composed of the same substance as the ectosarc, exhibiting little disposition either to ramify or coalesce, although a movement of particles adherent to their exterior is often to be distinguished. The type of this order is Actinophrys.

"III. LOBOSA.-More complete differentiation of the protoplasmic substance into endosarc and ectosarc, the former being a slightly viscous granular liquid, and the latter approaching the tenacity of a membrane; a nucleus and contractile vesicle; pseudopodia few and large, being in reality lobose extensions of the body which neither ramify nor coalesce, having welldefined margins, and not exhibiting any movement of granules on their surface, the circulation in their interior being entirely dependent on the changes of form which the body undergoes as a whole."

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As regards those "fundamental potentialities of each type -which, according to Dr. Carpenter, find a much more accurate physiological expression in the "form, proportions, and general arrangement of the pseudopodial extensions" than in the definite step-by-step advance from the simplest condition of the body-substance, observable in the Foraminifera (in which there is only the faintest foreshadowing of any thing akin to reproductive organization*), to the intermediate stage, in which this foreshadowing shows itself in the shape of a centralized but still imperfectly aggregated mass, and, finally, to the highest stage, in which the reproductive gemmules assume the concrete form of a distinct specialized nucleus (the culminating point being marked, at the same time, by the association of the nucleus with a specialized respiratory organ,

*It was shown by me that the "yellow cellules" of MM. Claparède and Lachmann, or more or less colourless homologues of these "cellules," occur in the sarcode of all the Rhizopods without exception, that in the lowest order they are formed, as it were, from minute granules uniformly distributed in the sarcode, that in the second and third orders they are formed by the splitting-up of the nucleus (which is in these a specialized reproductive organ), but that in all three orders they constitute the sarcoblast, or, in other words, the earliest visible embodiment of the young organism. See Ann. & Mag. Nat. Hist., June 1863 (where these bodies are figured), Dec. 1863, March 1864; and Quart. Journ. Micr. Science, July 1865.

namely the contractile vesicle)-I venture to say that however plausible Dr. Carpenter's hypothesis may be, it finds no response in nature. And I maintain that we are furnished with the most complete proof that could be desired of the invalidity of the characters derived from the pseudopodia for purposes of ordinal classification, in the passage from Dr. Carpenter's own writings quoted at p. 164. At all events I confess that it is quite beyond my humble powers to reconcile the admissions there made on Dr. Carpenter's part with his allegation, already quoted, that "the sarcode bodies of his three types Amaba, Actinophrys, and Gromia present three distinct stages in the differentiation of the protoplasmic substance of which they are composed," and that "the lines of demarcation thus drawn are as precise as in any other great natural group, between the three aggregations of forms which assemble themselves round the three well-known types" above named.

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But in order to prevent all misconception on this very important question, I must request attention to another extract from Dr. Carpenter's observations on the Systematic Arrangement of the Rhizopods (Nat. Hist. Rev. 1861, p. 461), where he states that "the ordinal designation Reticularia is meant to express the reticulose arrangement of the pseudopodial extensions, which is its distinguishing character.' And again, at page 463, he says that "the radiating pseu dopodia of Acanthometra correspond precisely in all their characters with those of Actinophrys, having the same rodlike tapering form, and same regular radiating arrangement, the same mutual isolation, the same slow movement of particles along their surface; some of them are, however, enclosed in tubular sheaths*, the differentiation of Acanthometra into ectosarc and endosare having obviously proceeded further than in Actinophrys.'

But although it is true that in Acanthometra the differentiation into ectosarc and endosarc has proceeded further than in Actinophrys, it is equally true that it has also proceeded further than in Amaba. But even stopping short at Dr. Carpenter's point, that it has proceeded further than in Actinophrys, how can this be reconciled with the statement that "the radiating pseudopodia of Acanthometra correspond

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* It was pointed out by me years ago that the appearance of tubularity in Acanthometra is altogether an illusion. There is no such thing as a tubular portion in the structure of these organisms. See a paper the Process of Mineral Deposit in the Rhizopods and Sponges," Ann. & Mag. Nat. Hist., Jan. 1864.

precisely in all their characters with those of Actinophrys "? The fact is that the pseudopodia of no other Rhizopods could possibly present appearances more distinct from each other, both as regards habit and arrangement, than those of these two organisms.

From what has already been brought forward it will be seen, I think, that the question under discussion, namely the error of making Gromia the type of foraminiferal structure, is reduced within very narrow limits. In short, it resolves itself into this-Is the practically imperceptible degree of organization, which Dr. Carpenter ascribes to the lowest or Reticularian order in his system, exemplified, as he pronounces it to be, in the type Gromia? Of course, if it be not so exemplified, and if it can be shown, on the one hand, that the so-termed typical pseudopodia of Gromia may be identical in all respects with the pseudopodia of the Foraminifera which Dr. Carpenter associates with Gromia, and, on the other hand, that Gromia, the reputed type of extreme primordial simplicity, besides having pseudopodia identical with certain Actinophryans, possesses both the nucleus and a contractile vesicle (which Dr. Carpenter allows to be distinctive of the highest degree of physiological development in the Rhizopod), there is, of course, on Dr. Carpenter's own showing, an end to his arrangement of these organisms on the basis upon which it has heretofore rested; and, what is more, there must be an end to every other classification of the Rhizopods which is based, in like manner with his, on characters derived primarily from the pseudopodia. There is no alternative, so far as I can see. And yet, as will presently appear, knowing these facts, Dr. Carpenter is quite unable to brace himself up sufficiently to make the necessary recantation candidly and ungrudgingly.

In my remarks "On the Distinctive Characters of Amaba" ('Annals,' Aug. 1863) it was mentioned that I had discovered a well-marked nucleus in Gromia, but had not, at that time, detected a contractile vesicle. In view, however, of the analogies existing between Gromia and the Amæbæ, so confident was I that the organ was there, that I expressed my conviction that I should speedily be able to trace the contractile vesicle also, adding that, if traced, the transfer of Gromia from the lowest to the highest order would of course be inevitable. Having for many months, both before and afterwards, spent many hours daily in watching the changes taking place in specimens of various genera of Rhizopods kept in tanks, I was fortunate enough in November of the same year to see the long-looked-for contractile vesicle in Gromia. This

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