776 INDEX. 
Will on gastrulation, 240 
on median elements of ganglia, 
481 
on sense of taste, 630 
on sexual cells in Aphis, 251 
Willis, views of, 99 
Wing, development of, 20, 161 
discs in Jarva, 84 
in nymph, 320 
extension of, 163, 202 
homology of, 160 
morphology of, 160, 163 
movements of, 163 
muscles of, 220, 283 
nervures of, 163 
organs, 620 
passive rotation of, 208 
posterior muscles of, 221 
rudiments of, in larva, 84 
structure of, 162 
sclerites of, 199 
typical form of, 162 
vibration, 203 
See also Flight 
Winter Flies, 6 
| Wistinghausen on tracheal capil- 
laries, 47 
Witlaczil on development of utero- 
vaginal tube, 703 
Wright on Anthony’s suckers, 394 
XIPHIDIUM, development of nervous 
system in, 480 
Xylocopa, maxilla of, 133 
YELK glands of Trematodes, 708 
segmentation, 13, 232, 237 
spherules, 13 
structure of, 683 
Yellow bodies of retina, 524 
Yung on brain of Arthropods, 442 
on reflex acts in Crustacea, 475 
Zaddach on number of primitive 
ganglia, 65 
on origin of blastoderm, 234 
Zoea stage of Crustacea, 30 
Zona radiata of germ ova, 719 
Zopfgraten, 29 
Zungenbein, 44 
