History of the Life of the most Simple Organism, a Moneron (Protomyxa aurantiaca). Compare vol. i. p. [184], and vol. ii. p. [53]. The plate is a smaller copy of the drawing in my “Monographie der Moneren” (Biologische Studien, 1 Heft, 1870; Taf. 1), of the developmental history of the Protomyxa aurantiaca; I have there also given a detailed description of this remarkable Moneron (p. [11]-30). I discovered this most simple organism in January, 1867, during a stay in Lanzarote, one of the Canary Islands; and moreover I found it either adhering to, or creeping about on the white calcareous shells of a small Cephalopod (vol. ii. p. [162]), the Spirula Peronii, which float there in masses on the surface of the ocean, or are thrown up on the shore. The Protomyxa aurantiaca is distinguished from the other Monera by the beautiful and bright orange-red colour of its perfectly simple body, which consists merely of primæval slime, or protoplasm. The fully developed Moneron is represented in Figs. 11 and 12, very much enlarged. When it is hungry (Fig. 11), there radiate from the surface of the globular corpuscule of plasm, quantities of tree-shaped, branching and mobile threads (pseudo-feet, or pseudo-podia), which do not become retiformly connected. When, however, the Moneron eats (Fig. 12), the mucous threads become variously connected, form net-works and enclose the extraneous corpuscule which serves as food, which the threads afterwards draw into the interior of the Protomyxa. Thus in Fig. 12 (above on the right), a silicious and ciliated Whip-swimmer (Peridinium, vol. ii. pp. [51], [57]), has just been caught by the extended mucous filaments, and has been drawn into the interior of the mucous globule, in which there already are several half digested silicious infusoria (Tintinoida), and Diatomeæ (Isthmia). Now, when the Protomyxa has eaten and grown sufficiently, it draws in all its mucous filaments (Fig. 15), and contracts into the form of a globule (Fig. 16 and Fig. 1). In this state of repose the globule secretes a simple gelatinous covering (Fig. 2), and after a time subdivides into a large number of small mucous globules (Fig. 3). These soon commence to move, become pear-shaped (Fig. 4), break through the common covering (Fig. 5), and then swim about freely in the ocean by means of a delicate whip-shaped process, like the Flagellata (vol. ii. p. [57], Fig. 11). When they meet a Spirula shell, or any other suitable object, they adhere to it, draw in their whip, and creep slowly about on it by means of form-changing processes (Figs. 6, 7, 8), like Protamœbæ (vol. i. p. [186], vol. ii. p. [52]). These small mucous corpuscules take food (Figs. 9, 10), and attain their full grown form (Figs. 11, 12), either by simple growth or by several of them fusing to form a larger protoplasmic mass (Plasmodium, Figs. 13, 14).
Plates [II]. and [III]. (Between pages 294 and 295, Vol. I.)
Germs or Embryos of four different Vertebrate Animals, namely, Tortoise (A and E), Hen (B and F), Dog (C and G), and Man (D and H). Figs. A, D, an early stage of development; Figs. E, H, a later stage. All the eight embryos are represented as seen from the right side, the curved back turned to the left. Figs. A and B are seven times enlarged, Figs. C and D five times, Figs. E and H four times. Plate [II]. exhibits the very close blood relationship between birds and reptiles; Plate [III]. that between man and the other mammals.
Plate [IV]. (Between pages 34 and 35, Vol. II.)
The Hand, or Fore Foot, of nine different Mammals. This plate is intended to show the importance of Comparative Anatomy to Phylogeny, in as much as it proves how the internal skeleton of the limbs is continually preserved by inheritance, although the external form is extremely changed by adaptation. The bones of the skeleton of the hand are drawn in white lines on the brown flesh and skin which surrounds them. All the nine hands are represented in the same position, namely the wrist (where the arm would be joined to it) is placed above, whilst the ends of the fingers or toes are turned downwards. The thumb, or the first (large) fore-toe is on the left in every figure; the little finger, or fifth toe is to the right at the edge of the hand. Each hand consists of three parts, namely (i.) the wrist (carpus), composed of two cross rows of short bones (at the upper side of the hand); (ii.) the mid-hand (metacarpus), composed of five long and strong bones (marked in the centre of the hand by the numbers 1-5); and (iii.) the five fingers, or fore toes (digiti), every one of which again consists of several (mostly from two to three), toe-pieces, or phalanges. The hand of man (Fig. 1), in regard to its entire formation, stands mid-way between that of the two large human apes, namely, that of the gorilla (Fig. 2), and that of the orang (Fig. 3). The fore paw of the dog (Fig. 4), is more different, and the hand or breast fin of the seal (Fig. 5) still more so. The adaptation of the hand to the movement of swimming, and its transformation into a fin for steering, is still more complete in the dolphin (Ziphius, Fig. 6). The extended fingers and bones of the central hand here have remained short and strong in the swimming membrane, but they have become extremely long and thin in the bat (Fig. 7), where the hand has developed into a wing. The extreme opposite of the latter formation is the hand of the mole (Fig. 8), which has acquired a powerful spade-like form for digging, with fingers which have become extremely short and thick. What is far more like the human hand than these latter forms, is the fore paw of the lowest and most imperfect of all mammals, the Australian beaked animal (Ornithorhynchus, Fig. 9), which in its whole structure stands nearer to the common, extinct, primary form of mammalia, than any known species. Hence man differs less in the formation of the hand from this common primary form than from the bat, mole, dolphin, seal, and many other mammals.
Plate [V]. (Between pages 84 and 85, Vol. II.)
Monophyletic, or One-rooted Pedigree of the Vegetable Kingdom, representing the hypothesis of the common derivation of all plants, and the historical development of the different groups of plants during the palæontological periods of the earth’s history. The horizontal lines denote the different smaller and larger periods of the organic history of the earth (which are spoken of in vol. ii. p. [14]), and during which the strata containing fossils were deposited. The vertical lines separate the different main-classes and classes of the vegetable kingdom from one another. The arboriform and branching lines indicate, in an approximate manner, by their greater or less number and thickness, the greater or less degree of development, differentiation, and perfecting which each class probably attained in each geological period. (Compare vol. ii. pp. [82], [83].)
Plate [VI]. (Between pages 130 and 131, Vol. II.)
Monophyletic, or One-rooted Pedigree of the Animal Kingdom, representing the historical growth of the six animal tribes during the palæontological periods of the organic history of the earth. The horizontal lines g h, i k, l m, and n o divide the five large periods of the organic history of the earth one from another. The field g a b h comprises the archilithic, the field i g h k, the palæolithic, the field l i k m the mesolithic, and the field n l o m the cenolithic period. The short, anthropolithic period is indicated by the line n o. (Compare vol. ii. p. [14.]) The height of the separate fields corresponds with the relative length of the periods indicated by them, as they may approximately be estimated from the relative thickness of the neptunic strata deposited between them. (Compare vol. ii. p. [22.]) The archilithic and primordial period alone, during which the Laurentian, Cambrian, and Silurian strata were deposited, was probably considerably longer than the four subsequent periods taken together. (Compare vol. ii. pp. [10], [20].) In all probability the two tribes of worms and Zoophytes attained their full development during the mid-primordial period (in the Cambrian system); the star-fishes and molluscs probably somewhat later (in the Silurian system); whereas the articulata and vertebrata are still increasing in variety and perfection.