be sufficient to show, what Burmeister, Dana, and Leydig, have proved in another way, that Rotifera are genuine Crustacea, and not worms. The vegetable character of most of the Anentera has been satisfactorily illustrated. I have not yet been able to arrive at a definite result respecting the Rhizopods, though they may represent, in the type of Mollusks, the stage of yoke-segmentation of Gasteropoda. From these remarks it should be inferred that I do not consider the Protozoa as a distinct branch of the animal kingdom, nor the Infusoria as a natural class."
"With reference to the Protozoa, first, it must be acknowledged that, notwithstanding the extensive investigation of modern writers upon Infusoria and Rhizopoda, the true nature of these beings is still very little known. The Rhizopoda have been wandering from one end of the series of Invertebrata to the other, without finding a place generally acknowledged as expressing their true affinities. The attempt to separate them from all the classes with which they have been so long associated, and to place them with the Infusoria in one distinct branch, appears to me as mistaken as any of the former arrangements; for I do not consider that their animal nature is yet proved beyond a doubt, though I have myself once suggested the possibility of a definite relation between them and the lowest Gasteropods.[1] Since it has been satisfactorily ascertained that the Corallines and Nullipores are genuine Algæ, which contain more or less lime in their structure, and since there is hardly any group among the lower animals and lower plants which does not contain simple locomotive individuals, as well as compound communities, either free or adhering to the soil, I do not see that the facts known at present preclude the possibility of an association of the Rhizopods with the Algæ. This would almost seem natural, when we consider that the vesicles of many Fuci contain a viscid, filamentous substance, so similar to that produced from the body of the Rhizopods, that the most careful microscopic examination does not disclose the slightest difference in its structure from that which mainly forms the body of Rhizopods. The discovery by Schultze of what he considers as the germinal granules of these beings by no means settles this question, since we have similar ovoid masses in Algæ, and since among the latter locomotive forms are also very numerous." In a note it is added, that "the recent investigations of Ehrenberg and J. Müller indicate a very close affinity between the Thalassicolæ, the Polycystinæ, and the Rhizopods; and the more I examine these enigmatical bodies, the more do they impress me as being allied to the lower Algæ and to the Sponges, rather than to any type of the animal kingdom."
"With reference to the Infusoria, I have long since expressed my conviction, that they are an unnatural combination of the most heterogeneous beings. A large number of them—the Desmidiacæ and Volvocinæ—are locomotive Algæ. Indeed, recent investigations seem to have established beyond all question the fact, that all the Infusoria Anenterata of Ehrenberg are Algæ. The Enterodela, however, are true animals, but belong to two very distinct types; for the Vorticellidæ differ entirely from all others. Indeed, they are, in my opinion, the only independent animals of that group; and, so far from having any natural affinity with the other Enterodela, I do not doubt that their true place is by the side of the Bryozoa, among the Mollusks, as I shall attempt to show presently. Isolated observations, which I have been able to make upon Paramecium, Opalina, and the like, seem to me sufficient to justify the assumption that they disclose the true nature of the bulk of this group. I have seen, for instance, a Planaria- ↑ Allusion is here made by Prof. Agassiz to the following passage, which occurs in a Paper on the Principles and Classification of the Animal Kingdom, published in the "Proceedings of the American Association for the Advancement of Science," Charleston, March, 1850:—
"Again, the position of the Foraminifera seems to me no longer doubtful. They are neither microscopic Cephalopoda nor Polype, as of late it has been generally thought best to consider them, but constitute a truly embryonic type in the great division of Gasteropoda, exemplifying, in the natural division, in a permanent condition, the embryonic state of development of common Gasteropoda, during which the bulk of the yolk passes through the process of repeated divisions."
