20 



DESIGN IN NATURE 



It may be useful to give here a few illustrative examples of spiral formations in plants and animals. 



As spiral plant and animal structures occur in great numbers througliout the work, it is only necessary, at this 

 stage, to emphasise the fact that spiral arrangements are fundamental, and that they make their appearance at 

 the very dawn of life, being found in seeds, seed-cases, flowers, fruit, adult plants and parts thereof ; in the ova 

 and spermatozoids of animals, in young and adult animals, and in many parts of animals, especially in the more 

 complex and highly differentiated animals. Spii'al movements are equally abundant. These make their appear- 

 ance in the spores and seeds of plants which, in many cases, move and swim freely about until they find a suitable 

 habitat, when they fix themselves permanently. 



Fig. 9 gives an accurate representation of the spiral forms and movements of certain Bacteria. 



Fig. 9. — A, Bnderium rcrmiforme. B, Bacteria from tlie river Thames (Proteus type) — young colony from jilate culture, greatly 

 enlarged (Maishall "N^'ard). At Fig. A, the spiral contortions and movements are very marked. At Fig. B, the spiral contortions 

 pursue two directions and revei'se, as in the tendrils of vegetable raari'ow, the passion-flower, the egg-purses of sharks, &c. ; one part 

 forming a right-handed, the other a left-handed spiral (the Author). 



The spiral movements are also seen in Infusoria and low animal forms generally. They can be traced without 

 difficulty from the lowest to the liighest animals, and, incredible as it may appear, fishes swim, birds fly, and 

 quadrupeds and bipeds walk, by double spiral or figure-of-8 movements, as was demonstrated by me somewhat 

 exhaustively in the years 1867, 1808, 1870, and 1873.i 



§ 6. Spiral Arrangements in Plants. 



The spiral arrangements in plants are at once striking and graceful, as the annexed illustrations show. 



Fi(_i. 10. 



Fro.. 11. 



Fio. 10. — Chara elastica : recent. Italy. — 



A. Ses.9ile oogonia between the divisions of the leaves of the female plant. 



B. Magnified transverse section of a branch, vifith five oogonia, seen from below (after Lyell). 

 Fio. 11.— 



A. Oogonium of Chara entire, composed of five cells wound round a large central cell in a spiral manner, with corona (a) 



B. Spiral spermatozoid of Chara separated from a cell. Shows two vibratile cilia (after J. H. Balfour). ' ' v A 



C. Fossil carpogonia of Chara. 6, Side view of Ghara Leniani, x 10 ; c, under view, showing sjiiral arrano-ement of cells 

 ],). Claira vmlicaijiniila, x 10. d, Side view ; t', under view, showing spiral arrangement of cells. " 



E. Chara lidideris, x 10. /, Side view ; g, under view ; and h, top view, showing spiral arrangenrents of cells ■ i one of thp 

 spiral cells detached (after Cuvier). ' ' 



The spirals shown at D and E of this figure resemble the spirals seen in nebulae (Plate viii.' 

 /, g), certain cones (Plate xi.. Fig. 1, bottom row), and the apex of the heart (Plate xvii.. Fig. 3, A). 



certain shells (Plate xiii., Fig. 1, 



1 I'joceedirigs Royal Institution of Great Britain, 1867 ; Transactions Linnean Society, 1868 ; Transactions Roval Societv FrU, 1 

 Anglo-American Science Series, 1873. ^' '^''^'"""r 



•gh, 1870 ; 



