INDEX 



975 



Skull, 668 



adult, relation of to embryonic chondro- 

 cranium, in chick, 678-679t 

 in frog, 676-677t 

 in human, 680-681t 

 development of, 669 

 Smith, P. E., 884, 885 

 Snake, differentiation of corpus luteum in, 

 84 

 garter, Thainnophis radix, sperm produc- 

 tion in, 23, 30 

 poison glands of, 617 

 Snell, G. D., 305 

 Sole, position of testes in, 7 

 Somatic mesodermal layer, 506 

 Somatoplasm, 1 14 



Somatopleure, definition of, 493, 530 

 Somites, in head region, 492 



relation to, primitive segmentation of de- 

 veloping body, 491 

 Somitic mesoderm, synonymous with epi- 



mere, 490 

 Spallanzani, 56, 281 

 Spalteholz, 704 

 Spawning-inducing, agent, 228 

 Specific organ-forming areas, history of 



concept, 343 

 Speidel, C. C, 733, 815, 819 

 Spemann, H., 381 

 Sperm, 16, 21 

 accessory, 32, 33 



activation of during fertilization, 212 

 agglutination of, 225 

 antifertilizin formation by, 230 

 chordate, types of, 140 

 conjugate, 147 



of grasshopper, 141 

 copulation path of, in frog's egg, 248 

 development, and luteinizing hormone, 

 41 

 summary, 170t 

 entrance into egg, 203, 243, 253 

 enzyme-protecting substances of, 34 

 flagellate, structure of, 147 

 head of, 142, 148 

 mammalian, kinoplasmic bead or droplet 



of, 765 

 metamorphosis of, 17, 147 

 morphogenesis of, in guinea-pig, 146 



in human, 146 

 non-flagellate, 141, 147 

 of frog, Rana pipiens, survival of, 198 

 of urodele amphibia, 143 

 older concept as parasites in seminal 



fluid, 213 

 penetration path of, 246 

 physiological differentiation of, 169 



Sperm — (Continued) 



physiological maturing, dependence upon 



LH, 43 

 pigmented trail of during fertilization, 



248 

 point of entrance of into egg of Styela, 



245 

 probable immotility of in epididymal 



duct, 180 

 production of, in bat, Myotis, 30 



in garter snake, Thainnophis radix, 30 

 in perch, Perca flavescens, 30 

 release from Sertoli cells by luteinizing 



hormone, LH, 43 

 secretions, 228 



spatulate, structure of, 142, 148 

 spermiogenesis of, 147, 151 

 spermioteleosis of, 147 

 storage of, 30 



structural parts of, and fertilization, 232 

 summary of activities of in initial stages 



of fertilization, 233 

 survival of, in female, genital tract, 197 

 survival outside male and female tracts, 



198 

 survival under artificial conditions, 198 

 transfer of from male to female, 189 

 transport of, estrogenic hormone influ- 

 ence on, 197 

 in mammal, 178 

 in vertebrates other than mammals, 



183 

 within female reproductive tract, 191 

 within male accessory reproductive 

 structures, 178 

 types of, 147 

 Sperm antifertilizin, and fertilizin of the egg 



in the fertilization process, 230 

 Sperm aster, division of, 247, 259 

 Sperm bead, 148 



"Sperm boat," of grasshopper, 141, 147 

 Sperm density, in semen, 32t 

 Sperm entrance into egg, time of in relation 



to maturation divisions, 144 

 Sperm extracts, effecting liquefaction of egg 



cortex, 229 

 Sperm number, and fertilization, 230 

 Sperm pronucleus, movements of during 



fertilization in Styela, 246 

 Sperm "ripeness," and ability to fertilize, 30 

 Sperm secretions, and agglutination of eggs 



during fertilization, 230 

 Sperm survival, and animal breeding, 198 

 Sperm transport, activities of efferent duc- 

 tules in, 180 

 by means of cloacal tail in Ascaphus 



triiei, 189 

 importance of muscle contraction in, 181 



