70 DESIGN IN NATURE 



PLATE XLIII 



Plate xliii. illustrates longitudinal and transverse cleavage and branching generally in plants, animals, and parts 

 thereof. 



Fio. 1.— Part of longitudinal section of the developing femur of the rabbit, magnified 350 diameters (after Klein and Noble Smith). 

 Shows longitudinal and transverse cleavage very distinctly, a, Rows of flattened cartilage cells ; b, greatly enlarged cartilage cells close 

 to advancing bone, the matrix between tliem being partly calcified ; c, d, bone already formed, the osseous trabecule being covered 

 with osteoblasts (e, e), except here and there, where a giant cell or osteoclast (/, /) is seen eroding parts of the trabeculse ; fj,h, shrunken 

 irregular cartilage cells ; i, i, vascular loops. The lower half of the figure shows the disappearance of the cartilage cells, the formation 

 of calcified cartilage matrix, and the deposition by the osteoblasts of secondary osseous substance. 



Fig. 2.~Nymphon ahyssorum (after Cuvier). Shows an extreme example of segmentation in body and limbs of deep-sea crab 

 (after Wyville Thomson). 



Fig. 3.— "Dead leaf" insect (Phylliimi sicdfolium, female). Shows resemblance to the venation and branching of leaves in its 

 flattened body and legs. The peculiarity in form in this insect and in the stick insect (Fig. 6 of this Plate) cannot be explained by 

 mimicry. Animals have no power to imitate or grow like anything but themselves. Like can only beget like. 



Fig. 4. — Egg of fish (Jarrabacm), showing the branching of the vessels in the vitelline circulation (after Dalton). 



Fig. 5. — Galeodes araneoides, a spider-like animal (family So^mgidx). Shows segmentation of body and great elongation and 

 branching of the limbs. The limbs might readily be mistaken for small dead branches. 



Fig. 6. — The stick insect {Proscopia nodula). So named from its marked resemblance to small dead branches (after Cuvier). 

 Shows segmentation and branching of body and legs. The peculiar form of this insect cannot be referred to mimicry. It can only 

 be explained by a common law of development. 



Fig. 7. — Acacia farnesiana (after Darwin). Aff'ords a good example of branching. 



A. Shows the leaves expanded during the day. B. The same folded at night. 



Fig. 8. — Portion of leaf of insectivorous plant (Drosophyllam Itisitanicum), (after Darwin). Shows peculiar mushroom-shaped glands. 



Fig. 9.— Chara, a plant allied to the Algte (after J. H. Balfour). Shows branching and spiral .formation. The arrows indicate 

 the direction of the spiral intra-cellular circulation. 



PLATE XLIV 



Plate xliv. illustrates striking resemblances between the convolutions of the human brain and the hard parts 

 of certain corals ; also between the hard parts of Venus's flower-basket and the spiral muscular fibres of the left 

 ventricle of the heart of the bird and mammal ; also between the spicules of sponges and certain crystals. 



Fig. 1. — External convolutions of the human brain. Shows folded plicate arrangement. 



FlG. 2. — Brain coral (Mseandrina cerchrifomiis), so named from the hard parts of skeleton greatly resembling the convolutions 

 of the human brain. The resemblance is so striking as to point to a common law of growth. It cannot be explained by mimicry 

 (photographed by the Author). 



Fig. 3. — Transverse section of upper part of tooth of Lalnjrintliodon jaeger), magnified, a, h. Margins of section (after Owen). 

 Shows a remarkable convoluted arrangement greatly resembling the human brain (Fig. 1 of this Plate) and the brain coral (Fig. 2 of 

 this Plate). 



Fig. 4. — The same tooth : natural size. The centre is the pulp cavity from which the processes of pulp and dentine radiate. The 

 combined radiation and plaiting and folding of the substance of the tooth is, in a way, unique. The letters a, h, indicate the position 

 from which the section shown in Fig. 3 was taken. 



Fig. 5. — Snow crystals as figured \>\ Scoresby. These are compound branched crystals, the branches being six in number. 

 Curiously enough the sponge spicules have also, in many cases, six branches or rays. The radiating arrangement is well marked in 

 both. Here again there seems to be a common law of development. 



Fig. 6. — Fertilisation of the ovum of an echinoderm (after Selenka). <(, Zona pellucida ; b, entrance of the spermatozoon into the 

 protoplasm of the vitellus (c), with radiating and concentric arrangement of its granules. Shows the fundamental nature of the 

 radiation and concentric arrangements. Here they present themselves at the very beginning of life. They are also found in all kinds 

 of adult animal structures (vide Plate v.), and in crystals and plant structures (Plates i., ii., iii., and iv.). 



Fig. 7. — Spicules of glass sponges (magnified). In the centre is a node of the diotyonic network of a ventriculite (Guide to Coral 

 Gallery, British Museum). Show beautiful .symmetrical forms greatly resembling crystals. Compare with the snow crystals delineated 

 at Fig. 5 of this Plate. 



Fig. 8. — Venus's flower-basket or glass sponge {liuplectella aqjcrgillum). Shows the hard parts of skeleton. These resemble .spun 

 glass, and form an intricate and exquisitely beautiful network of longitudinal, transverse, and oblique spiral fibres, which may not 

 inaptly be likened to the spiral muscular fibres forming the left ventricle of the heart. The arrangement in both cases consists of 

 layers, the spiral elements of which cross each other at various angles to form structuies remarkable for their lightness and strength. 

 (Compare with Figs. 6 and 7 of Plate xcvii. ; and the first eight Figs, of Plate xcviii., where dissections and models of the heart are given.) 

 a, Longitudinal portions of skeleton ; h, .■, oblique spiral portions ; d, transverse portions (photographed by the Author). 



