INDEX 



Generic and specific names are printed in italics. All numbers refer to pages. 

 The numbers in boldface type designate pages on which the reference is to 

 an illustration or the legend of an illustration. Where a figure and a text 

 reference appear on the same page, the page reference is not in boldface type; 

 thus, not every reference involving an illustration is given in boldface type. 



A cells, 120 



A substance, 65, 199 



Abdomen, 92 



Abdominal cavity, see Peritoneal cavity 



Abiogenesis, 259 



Absorption, 74-76; in invertebrates, 513 



Acanthella larva, 355 



Acanthocephala, 216, 219, 221, 344, 354-356, 



533 

 Acanthocephaliis, 355 

 Acanthor larva, 354, 355 

 .Accessorv glands, 122, 130 

 Acclimatization to prevailing conditions, 605 

 Accommodation, visual, 106 

 Acellular animals, 230 

 Acerenlulus barberi, 458 

 Acetvl coenzvme A, 36, 38 

 Acetylcholine, 98, 99, 113, 115 

 Achatinellidae, 652 



Acheulian cultural epoch, hand ax of, 645 

 Achondroplastic dwarfism, 118 

 Acinar cells of pancreas, 1 17, 120 

 Aaneta, 258 



Acoela, 316, 327; reproductive system, 532 

 Acoelomata, 219, 221, 343 

 Acoelomate bilateria, 222 

 Acontia, of Metridium, 306 

 Acquired characters, 646 

 Acraniata, 216, 539, 541, 545-553 

 Acromegaly, 118 

 Acrosome, 137 

 ACTH, 118, 122 

 Actin, 1 13 



Aclinophrys, 230, 236, 237 

 Actinopoda, 230, 236 

 Activation, 142 

 Active transport, 74, 84, 112 

 Actomyosin, 1 13 

 Adaptation, by changes in tolerance, 605; to 



environmental conditions, 595 



Adaptive radiation, of marsupials, 608, 609; 

 on oceanic islands, 632; principle of, in 

 mollusks, 393 



Addison's disease, 122 



Adductor muscles, of pelecypods, 370, 379 



Adenohypophysis, 118 



Adenosine triphosphate, 35, 36, 37, 75, 84, 113 



Adhesive cells, of Ctenophora, 310 



Adipose tissue, 61, 63 



Adjuster neurons, 98, 101, 524; in annelids, 

 409, 410 



Adrenal cortex, 121; hormones of, 26, 121 



Adrenal glands, 95, 117, 121 



Adrenal medulla, 117, 121 



Adrenaline, 113, 121 



Adrenocorticotropic hormone, 118, 121 



Aedes, 474, 476 



Aerobic phase, 36 



Afferent neuron, 98, 100; in annelids, 409, 410 



Africa, and ancestral proboscideans, 628; pre- 

 human stages in, 638; wild horses of, 625 



African ape man, 640 



African sleeping sickness, 463 



Agametes, of Mesozoa, 270 



Agancia agariates, 309 



Agassiz, Louis, 633 



Age of Amphibians, 562, 592 



Age of Fishes, 592 



Age of Invertebrates, 592 



Age of Mammals, 567, 591, 592 



Age of Man, 592 



Age of Reptiles, 565,592 



Agnatha, 216,541,555 



Agranular reticulum, 21 



Air, normal composition of, 599 



Air breathing, in early vertebrates, 561 



Air passages, 55, 155 



Alarm, life cycle, 332 



Alaska, earlv man in, 644 



Albinos, 199 



679 



