EVIDENCES OF DESIGN IN REPRODUCTIVE ELEMENTS 157 



PLATE LXII (continued) 



Fig. 8.— Spermatocyte of Proteus (Hermann), ii, Nucleus in the spirem or thread stage ; ti, attraction -sphere with rod-shaped 

 bodies and single centrosome. Figs. 5, 6, 7, and 8 illustrate concentric, radiating, and reticular arrangements. 



Fig. 9. — Nucleus from crypt of Lieberkiihn in Salamander (Heidenhain). Contains three plasmosomes or true nucleoli (n'); also 

 chromatin net- work (c) with some fine linin-threads (a). 



Fig. 10. — Remarkable permanent spirem-nucleus from salivary gland of larva of chirononius ; chromatin arranged in a single 

 thread with chromatin discs terminating at either end in a true nucleolus or plasmosome (Balbiani). Shows spiral arrangement of a 

 kind. 



Fig. 11. — Section of nephridian cell of leech (Clepsine) as drawn by Arnold Gray, n, Nucleus invested with chromatin membrane, 

 containing granules and a single nucleolus with vacuoli (v) ; v', v', large vacuole in centre of cell filled with watery fluid ; c, reticulum 

 formed by cytoplasm and containing centrosomes, well marked on peripheral zone. 



Fig. 12. — Spinal ganglion-cell of frog (Lenhossek). n, Nucleus with intensely chromatic nucleolus (n') and pale linin-network 

 with chromatin rounded granules (c) ; </, dark cytoplasmic masses (chromophilic granules) with a slightly concentric arrangement ; 

 h, centrosome, not very distinctly seen ; i, two connective tissue cells. The minute anatomy of the nerve cell is by no lueans simple. 



Figs. 13, 14, and 15. — Metaphase and anaphases of mitosis in cells (spermatocytes) of the salamander (Drviner). 



Fig. 13. — Metaphase. Shows spindle arrangement of fibres (s) ; centrosomes (c, c'), asters (a, a'), and two chromosomes {d, d'), attached 

 to contractile mantle-fibres at outside of spindle (6). 



Fig. 14. — -Anaphase. Shows divergence of the daughter-chromosomes (d), exposing the central spindle at the interzonal fibres (6) 

 with contractile fibres ; centrosomes (c, c'), and asters (a, a'), with concentric markings. This figure illustrates radiating and concentric 

 plus looped arrangements. 



Fig. 15. — Later anaphase. Fully exposes central spindle-fibres (s) ; also the contractile or mantle-fibres (m, m'), attached to the 

 chromosomes (d, d') ; a, a', asters ; c, c', centrosomes. The cell is now about to divide. 



PLATE LXIII 

 Plate Ixiii. illustrates spherical, concentric, radiating, branched, and segmented arrangements in the egg. 



Fig. 1.— a. Ovarian egg of the sea urchin {7'oxopneustes) magnified 500 diameters (Wilson), cjv, Germinal vesicle or nucleus, 

 containing an irregular discontinuous network of chromatin ; r/s, germinal spot or nucleolus deeply stained with hsematoxylin ; 

 cb, naked cell-body composed of a regular network, the threads of which consist of irregular rows of minute granules or microsomes. 



B. Spermatozoon or male element, also enlarged 500 diameters. 



Figs. 2 and 3. — Eggs of the annelid Nereis, before and after fertilisation ; magnified 250 diameters (Wilson). 



Fig. 2. — Before fertilisation. The large germinal vesicle or nucleus (gv) occupies a central position, and contains a network of 

 chromatin in which are five small dark bodies, the quadruple chromosome groups or tetrads, in process of formation : also a double 

 germinal spot (gs) composed of a chromatic and an achromatic sphere. The egg of the Nereis is laden with yolk consisting of clear 

 deutoplasm- spheres (d) and drops of fat (/) ; no deutoplasm being found in the peri-vitelline layer (jj). As reproduction proceeds 

 the tetrads of the germinal vesicle become more pronounced ; the network in which they are contained disappearing. This figure 

 illustrates concentric and spherical arrangements. 



Fig. 3. — Some time after fertilisation — egg about to divide. The deutoplasm (d, d') now occupies lower portion of egg, and the 

 peri-vitelline membrane has disappeared. The mitotic figure is also formed and the chromosomes (c) are dividing, pb, Polar bodies ; 

 a, asters. The changes consequent on fertilisation are very marked, and point to progressive development and differentiation. 

 Fig. 3 illustrates radiating and spherical arrangements. 



Figs. 4, 5, 6, and 7. — Young ovarian eggs with yolk-nuclei and deposits of deutoplasm. 



Fig. 4. — Myriopod {Geophilus) with one yolk-nucleus (yn), deutoplasm (d), and germinal vesicle (gu) as figured by Balbiani. 

 Shows concentric and spherical arrangements. 



Fig. 5. — The same with several yolk-nuclei (yn, yn), germinal vesicle (gv), and attraction-sphere (s). 



Fig. 6.— Fish (Scorpxna) with deutoplasm (d) forming a ring round the germinal vesicle (gv), with irregular mass of " eliminated 

 chromatin" as delineated by Van Bambeke. Shows well-marked concentric arrangements. 



Fig. 7.— Ovarian egg of a young duck, three months old, displaying a yolk-nucleus (yn), a germinal vesicle (gv), deutoplasm (d), 

 and an investing capsule (/), as figured by Mertens. Shows concentric and segmented arrangements. 



Figs. 8 and 9.— The middle phases of mitosis in the first cleavage of the Ascaris-egg as represented by Boveri. 



Fig. 8.— Closing prophase, the equatorial plate forming. (■, c ', Centrosomes ; a, a', asters. Shows radiating, concentric, and 

 spindle arrangements. 



Fig. 9.— Metaphase ; the equatorial plate (ep) completed— viewed from before, the four chromosomes divided. Centrosomes, 

 asters, and spindle, as in Fig. 8. pb. Polar bodies. It would be difficult to find a finer example of radiating and concentric 

 arrangements than is here furnished. 



