The invincible obstinacy with which Ehrenberg maintained his preconceived opinion of the high organisation of the Radiolaria, and entirely ignored the contrary observations of other naturalists, is explained by the consistency with which he held to the end the "principle peculiar to himself of the universally equal development of the animal kingdom" (L. N. [16], p. 7). From the complicated arrangement of their siliceous shells he concluded that the animals inhabiting them must possess a structure correspondingly complex, and nearly related to that of the Echinodermata (Holothuria). Like all other animals the Radiolaria must possess systems of organs for locomotion, sensation, nutrition, circulation, and reproduction. Whilst Ehrenberg originally interpreted the Polycystina as siliceous Infusoria polygastrica, and regarded them as compound Arcellina, he afterwards classed them sometimes with the Echinodermata (Holothuria), sometimes with the Bryozoa, sometimes with the Oscillaria (see L. N. [41], p. 336). Although a decided opponent of the cell-theory he called them "multicellular animalcules" (Polycystina), interpreting the pores of the siliceous shell as cells. To-day the opposite term (Monocystina) might be adopted to express their unicellular organisation. It was a remarkable irony of fate that in the self-same year (1838) in which Schwann of Berlin made by his foundation of the cell theory the greatest advance in the whole of Biological Science, that Ehrenberg, all his life the most zealous opponent of that theory, published his great work on the Infusoria, and at the same time established the "family of multicellular animalcules or Polycystina" (L. N. [16], p. 4).
The "short systematic survey of the genera of cellular animalcules" given by Ehrenberg in 1875 (L. N. [25], p. 157), is only a new edition, increased by sixteen genera, of his first systematic arrangement of the Polycystina of 1847 (L. N. [4], p. 53). Since I have already given a full discussion of this in my Monograph (L. N. [16], pp. 214-219), I need only here remark that a correct understanding of his very inadequate generic diagnoses is only possible by the aid of his figures. Relying upon these I have retained almost all Ehrenberg's genera, although entirely new definitions of most of them have been necessary.
The same is true also of the two orders which Ehrenberg distinguished in his class of "Zellenthierchen." The first order is constituted by his "Netzkörbchen" (Monodictya or Nassellaria) formerly known as "Polycystina solitaria"; they include our Cyrtoidea, the greater part of Hertwig's Monopylea. Ehrenberg's second order is the "Schaumsternchen" (Polydictya or Spumellaria), previously called "Polycystina composita"; they include the Peripylea of Hertwig, as well as the Spyridina (our Spyroidea), which belong properly to the Nassellaria. Although Ehrenberg's statements regarding the organisation of both these orders were quite erroneous, and his knowledge even of the structure of their shells very defective, I still thought it advisable to retain his names for the groups, since they constituted his one successful effort in the systematic treatment of the Radiolaria (compare L. N. [41], p. 336).
The sketch of a systematic arrangement of the Radiolaria (L. N. [37]), which I published in 1881 on the basis of the study of the Challenger Radiolaria, resembles, in respect of seven orders being distinguished, the new system which R. Hertwig founded in 1879, in consequence of the variations which he discovered in the structural relations of the central capsule (L. N. [33], p. 133). It differs, however, inasmuch as his Sphærozoea (my Polycyttaria) are here divided into two orders, Symbelaria (Collosphærida) and Syncollaria (Sphærozoida). In that sketch too I separated for the first time the two subclasses Holotrypasta (Porulosa) and Merotrypasta (Osculosa). The fifteen families established by Hertwig were then raised to twenty-four. The six hundred and thirty genera, which I then distinguished, are still for the most part retained, some, however, in a restricted sense, or with amended definitions.
The differential characters of the orders and families of the Radiolaria, given in the Prodromus in 1881, were amended in a further communication which I gave in 1883 regarding the orders of the Radiolaria (L. N. [46], p. 17). There I reduced the seven orders to four, the structural relations of the central capsule being precisely the same in the Polycyttaria and Collodaria as in the Peripylea. The survey of the affinities of the class was thus rendered much simpler and clearer, and the hypothetical genealogical tree, which I then published, has been still further carried out in Chapter VI. of the present Introduction (see §§ [153]-[200]).
253. General Survey of the Growth of our Systematic Acquaintance with the Radiolaria from 1834 to 1885.
1834. Meyen (L. N. [1]) describes 2 genera and species of Collodaria:—Sphærozoum fuscum and Physematium atlanticum.
1838. Ehrenberg (L. N. [2]) founds the family Polycystina upon 3 fossil genera (with 6 species):—Lithocampe, Cornutella, Haliomma.
1847. Ehrenberg (L. N. [4]) publishes his preliminary communications regarding the fossil Polycystina of Barbados and distinguishes 282 species, distributed in 44 genera and 7 families. In the tabular view of the genera he distinguishes two orders:—I. Solitaria—(1) Halicalyptrina, (2) Lithochytrina, (3) Eucyrtidina; and II. Composita—(4) Spyridina, (5) Calodictya, (6) Haliommatina, (7) Lithocyclidina (compare L. N. [16], pp. 214-219).
1851. Huxley (L. N. [5]) gives the first accurate account of living Radiolaria, and describes 2 species of the genus Thalassicolla (nucleata and punctata); under the latter are included 4 genera of Sphærozoea:—Collozoum, Sphærozoum, Collosphæra, Siphonosphæra (compare L. N. [16], pp. 12-14).