INDEX 



229 



Morgan, T. H., 58, 91 



Morrill, C. V., 166, 167, 170, 171 



Mortensen, 184 



Miiller, J., 184 



Murray, J. J., 202 



Non-axiate reproduction, 212-14 



Ophionotus hexactis, 184 

 Oshima, H., 183-85, 203 



Paedogenesis, 213, 214 

 Panum, P. L., 7 

 Paracopidomopsis, 218 

 Parasite and autosite twins: in 



fishes, 45, 46; in starfishes, 26, 



27 

 Parthenogenetic twins, in Patiria, 



12, 13 

 Patina miniata, 11-27, 180-82 

 Patterson, J. T., 61, 89, 100-102, 



104, io8-i6, 118-20,127,218,219 

 Pelobaks fuscus, 94 

 Petromyzon planeri, 98 

 Physiological isolation : a cause of 



twinning, 5-8, 69, 70; the 



common feature of modes of 



reproduction, 214, 215 

 Placentae of human one-egg twins, 



142, 144, 145 

 Polyembryony, i, 9, 103; versus 



twinning, 218, 219 

 Pristiurus, 98 



Pterostichus miihlfeldii, 193 

 Pygopagi, 122, 126 



Rauber, A., 7, 38-41 

 Reproduction, modes of, 206, 207 

 Retarded development, the pri- 

 mary cause of twinning, 14 

 Runnstrom, J., 184 



Saint-Hilaire: E. G., 75; 1. G., 7 

 Schatz, F., 137-58, 165 



Schmitt, F., 39 



Schultze, O., 91, 92 



Shull, A. F., 206, 207 



Siamese twins, 167 



Situs inversus viscerum, 7, 9, 50, 



69, 74, 92, 121, 136, 140, 157, 



164-79 



Situs rarior, 164 



Situs solitus, 164, 188, 189 



Situs viscerum transversus, 164 



Solito inversus, 164 



Spaeth, J., 136, 137, 164 



Spemann, H., 92, 175-78 



Spina bifida: in fishes, 42; in 

 frog, 93 



Stenotomus chrysops, 190 



Stockard, C. R.: 7, 27, 39, 46-48, 

 54, 71, 72, 75, 88, 108, 132, 133, 

 139; theory about twinning and 

 alternation of generations, 216, 

 217; theory of causes of twin- 

 ning in armadillo, 103-5, ii9» 

 120; theory of origin of double 

 monsters, 61-68 



Streeter, G. L., 126-31 



Strongylocentrotus lividus, 184 



Subnormal development, causes of, 

 in twins, 49, 50 



Sumner, F. B., 58 



Swett, F. H., 171-73 



Sylvestri, 218 



Symmetry, rules of, 194 



Symmetry reversal; general the- 

 ory of, 185-89; in echinoderm 

 larvae, 179-85; in fish twins, 

 168-75; ui human twins, 164- 

 68; in Triton, 175-79 



Tannreuther, G. W., 80, 82-86 

 Tautogolahrus adspersus, 190 

 Third circulation, in placenta of 



human one-egg twins, 142 

 Thoracopagi, 126 

 Toda, K., viii 

 Tornier, 92 



