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RADIATING AND BRANCHING ARRANGEMENTS -ji<br />
PLATE XLV<br />
Plate xlv. illustrates radiating and branching in plants and animals and parts thereof.<br />
Fig. 1.—A dicotyledonous seedling with an ascending and descending axis (Hentrey). Shows branching above and below ground.<br />
Fig. 2.—The screw pine (Pandanus odoratissimus) with adventitious roots supporting the trunk (Henfrey). Shows radiation and<br />
branching at either end of trunk.<br />
Fig. 3.—The mangrove tree (Rhizophora), supported as it were upon piles ; the roots rjiising up the trunk (J. H. Balfour).<br />
Shows radiation and branching in two directions.<br />
Fig. 4.—Venus's fly-trap (Dioneea muscipula), a sensitive, insectivorous plant. Shows radiation and division in the leaves.<br />
a, Leaf fully expanded ; h, ditto partly closed ; c, ditto closed (J. H. Balfour).<br />
Fig. 5.—Paramecium (after Masterman). Shows radiation and division of surface, a, Mouth ; h, anus ; c, cilia ; d, trichocyst ;<br />
e, contractile vesicle ; /, medulla ; g, cortex ; h, thread of trichocyst ; i, food-vacuole ; j, micro-nucleus ; k, macro-nucleus.<br />
Fig. 6.—Larva of calcareous sponge at the Gastrula stage (Haeckel). Shows radiating and branching in a low form at a very early<br />
period of development. The larva consists of an outer and inner cell layer, and forms a pouch with a mouth.<br />
Fig. 7.—Diagram of human ovum and placenta (after Fothergill). Shows well-marked radiating and branched arrangement.<br />
a, Epithelium or chorion ; b, connective tissue ; c, epithelium or amnion.<br />
Fig. 8.—Villi of intestine of mare and sheep (after Carpenter). Show branching of villi and of the blood-vessels and lymphatics<br />
of villi. The branching is minute and complicated.<br />
A. Villi of mare, a, Epithelium ; b, artery ; c, vein ; d, capillaries ; e, lacteals.<br />
B. Villus of sheep. Same lettering as in A.<br />
C. Vertical section through one of Peyer's patches in the lower part of the ileum of the sheep, a, a, Lacteal vessels in the villi<br />
b, b, superficial layer of the lacteal vessels ; c, c, deep layer of the lacteal vessels ; d, d, afferent lacteals provided with valves ; e, Peyer's<br />
gland ; /, circular muscular layer of the wall of the intestine ; g, longitudinal muscular layer of ditto ; h, peritoneal layer.<br />
PLATE XLV<br />
Plate xlvi. illustrates the first appearance and mode of formation of limbs. This is a form of budding, division,<br />
and branching. The longitudinal division is seen in the fins and tails of fishes, the several kinds of flippers, and the<br />
fore-arms, legs, and digits of bipeds and quadrupeds : the transverse division is seen in the vertebral column or<br />
backbone.<br />
Fig. 1. Lepidosiren annectens (Owen) ; Protopterus annectens (Giintber). Show branching filamentous appendages, a, Filamentous<br />
anterior extremities or pectoral fins ; b, filamentous posterior extremities or ventral fins ; c, scapulo-coracoid bone with<br />
jointed cartilaginous ray of pectoral fin ; d, pelvic cartilage and jointed cartilaginous ray of ventral fin (after Owen and Giinther).<br />
Fig. 2.—Siren {Siren lacertina), Amphiuma (Amphiuma tridactylum), and Menobranchus (Menobranchus lateralis) ; revealing rudimentary<br />
limbs, and branching thereof.<br />
A. Siren. Shows rudimentary anterior extremities with imperfect digits.<br />
B. Amphiuma. Shows rudimentary anterior and posterior extremities, each with three digits.<br />
0. Menobranchus. Shows more highly developed anterior and posterior extremities with four digits (after Cuvier and from<br />
nature).<br />
Fig. 3.—Development of the human embryo from the third to the seventh week. Shows division and segmentation of the body<br />
(visceral arches and spinal column), the growth of the head and body, and the growth and budding of the limbs. Tlie lettering is<br />
the same in all the figures.<br />
A. Three and a half weeks embryo, a, Rudimentary vertical column terminating in a caudal process or tail ; b, budding, unformed,<br />
superior limb ; c, ditto, inferior limb ; d, branchial arches ; e, rudimentary umbilical or nourishing cord ; /, head beginning<br />
to assume shape.<br />
B. Four weeks embryo. In this the spinal column (a) is a little more pronounced than at A, especially the caudal portion. The<br />
branchial arches (d) are also more defined, and the upper (6) and lower (c) extremities are increased in size.<br />
C. Four and a half weeks embryo. In this the parts are becoming more defined.<br />
D. Kive weeks embryo. In this the parts referred to under A are altering slightly in appearance, the left superior extremity (b)<br />
developing a rudimentary hand and five digits or fingers, the head (/) being increased in volume, and the spinal column (a) being less<br />
prominent from being partly covered in.<br />
a foot.<br />
E. Five and a half weeks embryo. The changes referred to under D are more pronounced, the posterior extremity (c) developing<br />
F. Six weeks embryo. In this the head and body have increased in size, and the segmentation of the spinal column has disappeared<br />
from being covered in. The left superior (6) and left inferior (c) extremities have grown, and the hands and feet, fingers and<br />
toes, are becoming more distinct. The digits on the feet, as on the hands, are five in number.<br />
G. Seven weeks embryo. In this the head and body are growing and assuming shape, the branchial arches (d) and the spinal<br />
column (a) being less obvious. The left superior (6) and left inferior (c) extremities are elongated and gradually assuming shape.<br />
The changes begun in the embryo, it need scarcely be stated, are completed in the fos?tns at full term, but need not be further<br />
described. Drawn for the present work by C. Berjeau,<br />
VOL. I.<br />
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