592 



INDEX OF SUBJECTS. 



Triamophorus, segmentation of, 168 

 Triopa clavigera, rhiuophore ti-ifid, 280 

 Triton, legs repeated, 555 

 Troglodytes, vertebras, 116; teeth, 202 

 Tropidonotus, vertebra?, 123 ; scales, 276 

 Trout, bulldog-headed, 58, 59; axial du- 

 plicity, 563 

 Tulip, Meristic Variation in, 60 

 Turbot, pigmentation of lower side, 467, 



470 

 Tardus, brachial plexus, 131 

 Turkey, digits, 393 



Twins, homologous, 559 ; Simultaneous 

 Variation of, as a case of Bi- 

 lateral Symmetry, 559 

 Siamese, peculiarities of, 560 ; 

 thoracopagous, 560 

 in Echinoderms and in Amphi- 

 oxus, 35 

 Typosyllis, double head, 564 



Uca una, extra parts in chela, 530 



Ulna, a second, 331 



Ulnar nerve, variations in composition 

 of, 136 ; a second, 333 



Uugulata, teeth, 243 ; digits, 360—390, 397 



Union, mediau, 458; of horns of Roe- 

 buck, 460; of eyes of Bee, 461; of 

 kidneys, 459; of tentacles of Limax, 

 460; of tentacles of Helix, 461; of 

 posterior limbs of Vertebrates, 459; of 

 digits in Ox, 383, 386; of digits in 

 Pig, 387—390 



Units, of Repetition, 556 



Uraetos, brachial plexus, 131 



Ureters, supernumerary, 278 



"Useless" parts, supposed variability of, 

 78 



Uterus, double, Darwin's comment on, 

 77 ; is a case of median division, 451 



Utility, fallacies of reasoning from, 12 



Uvula, division of, 451 



Vanessa atalanta, colour- variation, 46 

 urticce, extra wing, 283 

 in, eye-spots, 299, 300 

 Variation, denned, 3 



the Study of, as a method 



of attacking the problem of 



Species, 6 

 Continuous and Discontinu- 

 ous, 15 

 Meristic and Substantive, 



distinguished, 23, 24 

 magnitude of integral steps 



affected by Merism, 25 

 about a Mean form, 37 

 perfection in, 60, 64 

 causes of, 78 

 Hoinceotic, 85, in vertebras, 



106; in Arthropoda, 146; 



in teeth, 272 

 Simultaneity of, in repeated 



parts, 303, 402, 425, 464 



Variations, minimal, questionable uti- 

 lity of, 16 

 Vertebrae, Meristic Variation in, 102 

 imperfect division, 103, 458 

 Homceotic Variation, 106 

 reduction in numbers, Man, 



111 

 numerical variation, 102 

 Man, 103, 106—116; Anthro- 

 poid Apes, 116; Bradypodi- 

 da?, 118; Carnivora, 122; 

 Reptilia, 123 ; Batrachia, 

 124; features of Variation 

 recapitulated, 127 ; correla- 

 tion with spinal nerves, 113, 

 115, 139, 145 

 Vesperus luridus, extra eye, 280 

 Veronica buxbaumii, numerous symme- 

 trical variations in, 76 ; illus- 

 trating variations of Bila- 

 teral Series, 448 

 Viverridae, teeth, 227—231 



Waigiu, female Phalanger maculatus 

 coloured like male in island 

 of, 254 

 Wall butterfly, variation in ocelli and 



neuration, 300 

 Water-pore, extra, in Bipinnaria, 466 

 Webs, between toes of Duck, absent, 401 

 Weevils, four visible joints in tarsus, 25 

 Wing, supposed to replace a leg in Zy- 



gccna, 148 

 Wings, supernumerary in Insects, 281 

 fore and hind, varying simul- 

 taneously in Lepidoptera, 293 

 quills of, varying with quills of 

 tail in Pigeons, 309 

 Woodpecker, Green, colour-variation, 43 



Xantho punetulatus, duplicity of index, 



542 

 Xiphopagous twins, transposition of 



viscera in, 560 

 Xylotrupes gideon, variation of horns in, 



38 



Yellow, variations of, 43-48, 73 

 Yew, yellow-berried, 47 



Zalophus californianus, molars, 243 



lobatus, premolars, 238, 242; 

 molars, 243 

 Zebra, repetition of stripes in, 26 

 Zeugopterus, white varieties, 467 ; varia- 

 tion in dorsal fin, 471 

 Zonabris quadripunctata, double (?) an- 

 tenna, 551 

 Zonites prceusta, extra antenna?, 522 

 Zygcena filipendulce, colour variation, 46 

 supernumerary wing, 

 148 

 minos, colours, 46; extra wing, 

 284 



