934 



Amby stoma maculatum (punctalum), xvii 

 cleavage in, 305 

 early, 306 

 Ambystoma mexicanum, xvii 



gills of, 639 

 Ambystoma punctatiim, limb-bud field in, 

 509 

 neural crest cells in, 464 

 Ambystoma tigrinum, sex reversal in, 890 

 Ameiiirus, facial nerve in, 825 

 Ameloblasts, 563, 611 

 Amia (bowfin), egg of, 309 

 egg membranes of, 310 

 male guarding young, 929 

 male reproductive duct in, 18 

 vertebrae formation in, 685 

 Amia calva, bowfin, xvii 

 air bladder of, 643 

 cleavage in, 309, 310 

 egg of, characteristics of, 203t 

 fertilization, site of, 203t 

 gastrulation in, 444 

 neurocranium, developmental stages of, 



670 

 sperm entrance into egg, place of, 203t 

 Amitosis, 281 

 Amnion, 902, 908, 909 

 fate of, 925 

 formation of, 910 

 Amniota, 902 



explanation of term, 909 

 heart, development of, 753 

 paired appendage rudiments in, 508 

 Amphiarthrosis, 695 

 Amphiaster, of first cleavage, 247, 259 



influence on polyspermy, 286 

 Amphibia, xvii 



anuran, definitive body form assumption 

 in, 884 

 gastrula of, beginning, 355 

 metamorphosis of, role of thyroid and 



pituitary glands in, 883 

 organ-forming area relationships at 

 end of gastrulation in, 460 

 coelomic changes in, 867 

 epidermal tube development in, 474 

 gastrula of, ectodermal potencies of, 414 

 gastrulation in, 406 



movements of parts of blastula during, 

 411 

 gill resorption in, 642 

 gymnophiona, blastulae of, 370 

 cleavage in, 312 

 gastrulation in, 444 

 intromittent organ of, 192 

 independent pericardial wall develop- 

 ment in, 871 

 myotome differentiation in, 714 



A mphibia — (Continued) 



skin of, characteristics of, 565 



vertebrae development in, 685 



vitelline membrane in, 167 



zona radiata in, 167 

 Amphioxus, xv 



anus formation in, 502 



blastopore closure in, 501 



blastula of, 356 



organization of, 342 



cleavage in, 288, 290, 342 



egg of, bilateral symmetry of, 162 



egg membranes of, 165 



emboly in, 402 



epiboly in, 403 



epidermal overgrowth of neural plate in, 

 502 



fertilization of, 247 



fertilization of egg in, 227 



gastrula, antero-posterior extension of, 403 



gastrulation in, 402, 404 

 resume of, 405 



germinal vesicle in, 136 



importance of end-bud growth in, 494 



maturation of egg in, 227 



mesoderm position in embryo of, 494 



mouth formation in, 502 



notochord position in embryo of, 494 



organ-forming areas in egg of, 161 



presumptive organ-forming areas of, 353 



production of twin embryos through iso- 

 lation of first two blastomeres in, 

 335 



skin of, origin of dermal component of, 

 559 



somite differentiation in, 504 



stages of development of, 503 



stomach area of, 621 



tubulation in, 494 



of entodermal area, 500 

 of mesoderm, 503 

 Amphioxus (Branchiostoma) lanceolatum, 

 egg, characteristics of, 203t 



fertilization, site of, 203t 



sperm entrance into egg, place of, 2031 

 Amphiuma, external gills of, 639 

 Amphiuma means, xvii 

 Amplexus, in frog, 201 



in toad, 185 

 Ampulla (Ampullae), 843, 854 



of vas deferens, 20 

 Anal membrane, 600 

 Anal opening, of mammals, 715 

 Analogy, 551 

 Anamniota, explanation of term, 909 



rudiments of paired appendages in. 508 

 Ancel, P.. 249 

 Anderson, D. H., 904 



