RADIATING AND BRANCHING ARRANGEMENTS -ji 



PLATE XLV 



Plate xlv. illustrates radiating and branching in plants and animals and parts thereof. 



Fig. 1. — A dicotyledonous seedling with an ascending and descending axis (Hentrey). Shows branching above and below ground. 



Fig. 2. — The screw pine (Pandanus odoratissimus) with adventitious roots supporting the trunk (Henfrey). Shows radiation and 

 branching at either end of trunk. 



Fig. 3. — The mangrove tree (Rhizophora), supported as it were upon piles ; the roots rjiising up the trunk (J. H. Balfour). 

 Shows radiation and branching in two directions. 



Fig. 4. — Venus's fly-trap (Dioneea muscipula), a sensitive, insectivorous plant. Shows radiation and division in the leaves. 

 a, Leaf fully expanded ; h, ditto partly closed ; c, ditto closed (J. H. Balfour). 



Fig. 5. — Paramecium (after Masterman). Shows radiation and division of surface, a, Mouth ; h, anus ; c, cilia ; d, trichocyst ; 

 e, contractile vesicle ; /, medulla ; g, cortex ; h, thread of trichocyst ; i, food-vacuole ; j, micro-nucleus ; k, macro-nucleus. 



Fig. 6. — Larva of calcareous sponge at the Gastrula stage (Haeckel). Shows radiating and branching in a low form at a very early 

 period of development. The larva consists of an outer and inner cell layer, and forms a pouch with a mouth. 



Fig. 7. — Diagram of human ovum and placenta (after Fothergill). Shows well-marked radiating and branched arrangement. 



a, Epithelium or chorion ; b, connective tissue ; c, epithelium or amnion. 



Fig. 8. — Villi of intestine of mare and sheep (after Carpenter). Show branching of villi and of the blood-vessels and lymphatics 

 of villi. The branching is minute and complicated. 



A. Villi of mare, a, Epithelium ; b, artery ; c, vein ; d, capillaries ; e, lacteals. 



B. Villus of sheep. Same lettering as in A. 



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 ; 



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 

 gland ; /, circular muscular layer of the wall of the intestine ; g, longitudinal muscular layer of ditto ; h, peritoneal layer. 



PLATE XLV I 



Plate xlvi. illustrates the first appearance and mode of formation of limbs. This is a form of budding, division, 



and branching. The longitudinal division is seen in the fins and tails of fishes, the several kinds of flippers, and the 



fore-arms, legs, and digits of bipeds and quadrupeds : the transverse division is seen in the vertebral column or 

 backbone. 



Fig. 1. — Lepidosiren annectens (Owen) ; Protopterus annectens (Giintber). Show branching filamentous appendages, a, Fila- 

 mentous anterior extremities or pectoral fins ; b, filamentous posterior extremities or ventral fins ; c, scapulo-coracoid bone with 

 jointed cartilaginous ray of pectoral fin ; d, pelvic cartilage and jointed cartilaginous ray of ventral fin (after Owen and Giinther). 



Fig. 2. — Siren {Siren lacertina), Amphiuma (Amphiuma tridactylum), and Menobranchus (Menobranchus lateralis) ; revealing rudi- 

 mentary limbs, and branching thereof. 



A. Siren. Shows rudimentary anterior extremities with imperfect digits. 



B. Amphiuma. Shows rudimentary anterior and posterior extremities, each with three digits. 



0. Menobranchus. Shows more highly developed anterior and posterior extremities with four digits (after Cuvier and from 

 nature). 



Fig. 3. — Development of the human embryo from the third to the seventh week. Shows division and segmentation of the body 

 (visceral arches and spinal column), the growth of the head and body, and the growth and budding of the limbs. Tlie lettering is 

 the same in all the figures. 



A. Three and a half weeks embryo, a, Rudimentary vertical column terminating in a caudal process or tail ; b, budding, un- 

 formed, superior limb ; c, ditto, inferior limb ; d, branchial arches ; e, rudimentary umbilical or nourishing cord ; /, head beginning 

 to assume shape. 



B. Four weeks embryo. In this the spinal column (a) is a little more pronounced than at A, especially the caudal portion. The 

 branchial arches (d) are also more defined, and the upper (6) and lower (c) extremities are increased in size. 



C. Four and a half weeks embryo. In this the parts are becoming more defined. 



D. Kive weeks embryo. In this the parts referred to under A are altering slightly in appearance, the left superior extremity (b) 

 developing a rudimentary hand and five digits or fingers, the head (/) being increased in volume, and the spinal column (a) being less 

 prominent from being partly covered in. 



E. Five and a half weeks embryo. The changes referred to under D are more pronounced, the posterior extremity (c) developing 

 a foot. 



F. Six weeks embryo. In this the head and body have increased in size, and the segmentation of the spinal column has dis- 

 appeared from being covered in. The left superior (6) and left inferior (c) extremities have grown, and the hands and feet, fingers and 

 toes, are becoming more distinct. The digits on the feet, as on the hands, are five in number. 



G. Seven weeks embryo. In this the head and body are growing and assuming shape, the branchial arches (d) and the spinal 

 column (a) being less obvious. The left superior (6) and left inferior (c) extremities are elongated and gradually assuming shape. 

 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 

 described. Drawn for the present work by C. Berjeau, 



VOL. I. ^ 



