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Show 144 LAWS OF VARIATiON. CHAP. V; 11 . to a tube. Hard parts seem the petals of the cof at ~~ng soft parts ; it is believed to affect the form ~ t t~ diversity in the shape of the by some authors t a t: emarkable diversity in the pelvis in bi~ds ~::~e: 1~t~ers believe that the shape shape of th~Ir. ki h ~l~man mother influences by presof the pelvis In !f e the head of the child. In snakes, sure t~e shap~ hl 1 the shape of the body and the macacnonrdeirn ogf tsow alclo w~igneg 'd t mine the position of several ~ er f tl t important viscera. o le most f the bond of correlation is very fre- The na ure o H'l . h quently qui.t e ob s cure. M· Is· Geoffroy St. I. aire as form.b ly remark e d ' that certain malcon·f orma'ttihon st very· tl d that others rarely coexist, WI ou our frequen y, an Wh t be more . able to assign any reason. a can b_emgl than the relation between blue eyes and deafsingu. ar ts and the tortoise-shell colour with the female ::;~ ~~afe~thered feet and skin between the outer to:s . '. and the resence of more or less down on t e m ~ge~~:ds when ~t hatched, with the future colour ~f tyho . g lumage . or again, the relation between the harr edu t epe th in th' e n' aked Turki.s h dog, t h oug h here phroi - banab ly homology comes into play ? w·I t h resp ecbt to t .s latter case of correlation, I t ln ·n k 1' t can h ard ly e acCliIa-dental that if we pick out the two orders of m~mma. which,are most abnormal in their der~l covermg, :~ Cetacea (whales) and Edentata ( armadilloes, sc~ly I eat ers, &c ·) , that these are likewise the most a norma in their teeth. h the im· I know of no case better adapted to s o~ . . portance of the laws of correlation in 'l~odify~n~h;:~ portant structures, ind~pendently ~f ut; It~e a~ifference fore of natural selection, than t at ~ Compo- betw' een the outer and I· nner fl. ower s .m somken ows the sitous and U mbelliferous plants. Every one CHAP. V. OORRELATION OF GROWTH. 145 difference in the ray and central florets of, for instance, the daisy, and this difference is often accompanied with the abortion of parts of the flower. But, in some Compositous plants, the seeds also differ in shape and sculpture ; and even the ovary itself, with its accessory parts, differs, as has been described by Cassini. These differences have been attributed by some authors to pressure, and the shape of the seeds in the ray-florets in some Compositoo countenances this idea; but, in the case of the corolla of the U mbelliferoo, it is by no means, as Dr. Hooker informs me, in species with the densest heads that the inner and outer flowers most frequently differ. It might have been thought that the development of the ray-petals by drawing nourishment from certain other parts of the flower had caused their abortion ; but in some Compositoo there is a difference in the seeds of the outer and inner florets without any difference in the corolla. Possibly, these several differences rna y be connected with some difference in the flow of nutriment towards the central and external flowers : we know, at least, that in irregular flowers, those nearest to the axis are oftenest subject to peloria, and become regular. I may add, as an instance of this, and of a striking case of correlation, that I have recently observed in some garden pelargoniums, that the central flower of the truss often loses the patches of darker colour in the two upper petals; and that when this occurs, the adherent nectary is quite aborted; when the colour is absent from only one of the two upper petals, the nectary is only much shortened. With respect to the difference in the corolla of the central and exterior flowers of a head or umbel, I do not feel at all sure that C. C. Sprengel's idea that the ray-floretB serve to attract insects, whose agency 1s highly advantageous in the fertilisation of plants of H |