INDEX 



519 



Median eye(s), 

 origin of 



concrescence of two gastrular invagi- 

 nations, 41 



defective growth of central region of 

 head, 37, 38 



degeneration resulting from disuse, 26 



displacement towards median plane, 

 26-28 



fusion of lateral paired eyes, 27 



fusion of median paired eyes, 26, 104, 

 328, 328-331, 331, 350, 360-362 



fusion of presumptive eye-rudiments, 



34 

 growth of eyes in contact with each 



other, 34, 36, 37, 38 

 impaired power of organisation, 30 

 incomplete separation, Diprosopus, 33 

 injurious environment, 38 

 loss of function and replacement by 



lateral eyes, 143 

 suppression of one member of a pair 

 of eyes, 175 

 of Petromyzon, 71, 187 

 of Pholidosteus, 329 

 in Planaria, 37 

 of Porthetis, 343 

 of Pterygotus, 135 

 of Rhinosteus, 329 

 of Rotifers, 89 

 of Salpa, 176, 177 

 of Scorpions, 132, 368, 370 

 of Tabanus, 26 

 of Titanosuchus, 339 

 tubercle, 139, 469 

 of Tretaspis, 139, 351 

 of Trilobites, 136 

 in Triton, 35 

 of Varanns, 247 

 of Xylocopa, 342 

 Medullary plate, 11 

 Megakesthetes, 355 

 Melanerpeton, 235 

 Melanin, 60, 78, 191 

 Melanoblasts, 60 



dermal, 61 

 Melanogen, 60 



Melanotic sarcoma of pineal body, 59 

 Membrane, 



external limiting, 206, 249, 255, 297 

 internal limiting, 206, 249, 255 

 Merostomata, 345, 349, 359, 380, 472 

 Mesoglia, 390 

 Mesosuchus, 268 



Mesozoic period, Dipnoi of, 221 

 Metameric organs in median plane, 187 

 Metamorphosis of proparenchyma cells, 



316 

 Meynert, bundle of, 187, 261, 310 



difference in size of right and left 

 bundles, 187, 468 

 Microglia, 386, 390 

 development of, 391 

 migration of, 391 

 relation to nerve-cells, 392 

 resting or fixed stage of, 392 



Mites, freshwater, 129 

 Mixosaurus atavus, 269, 270 

 Mole, eyes of, 239 

 Molge cristata, 227 

 Molluscoida, eyes of, 91 

 Molluscs, 



eyes of, 147 



pigmentation of eyes of, 67 

 Moloch horridus, 242, 273 

 Monorhina, 347 



fusion of primarily paired organs, 47 

 Monotremes, 323 

 Monster(s), 



double headed, 43 



duplicitas anterior, 33 



duplicitas cruciata, 34, 35 



duplicitas posterior, 31, 32 



experimental production of, 37 



occurrence of in domestic animals, 35, 

 36 



single headed, 37 



Rhinocephalus, 30, 36 

 Mordacia mordax, 198 

 Mosaic, arrangement of cells, 315, 432 

 Mosasaurida, 285 



Moulting, of chitinous exoskeleton, 474 

 Muco-cartilage of Ammocoetes, 192 

 Miiller, fibres of, 191 

 Muller's larva, paired ocelli of, 84 

 Murex, 49 

 Muscle(s), 



ciliary, 437 



of dilator pupillas, 61 



of eyes of decapod molluscs, 50 



of eyes of Hydrachnida, 129 



in eyes of octopoda, 50 



in optic stalk of Astacus, 16 



pupillary, 437 



of sphincter pupilla;, 61 



smooth, 431 



transversely striated, 432 

 Muscular tone, increase of, 438 

 Musculature, somatic of head-region, 192 

 Mussel, 147 



Myliobatis, anterior position of end- 

 vesicle, 210 

 Myxine glutinosa, 187, 198 

 Myxinoidea, 198, 344 



Nasohypophyseal opening, 328, 344, 470 

 Nautiloid tetrabranchiata, extinct forms of, 



163 

 Nautilus, 147, 152, 153, 161, 162, 355, 356 

 Nautilus pompilius, 162 



internal skeleton of, 163 

 Necturus maculatus, 224 

 Nemathebuinthes, eyes of, 86 

 Nepthys, absence of eyes in, 100 

 Nereis, paired eyes of, 96 

 Nerve cells, 



interependymal, 388 



intraependymal, 388 

 Nerve-cords, 



median, 82 



paired lateral, 82 



