Heredity, Variation, and the Appearance of Diversities during the Vegetative Reproduction of ARCELLA DENTATA.

PAGE INTRODUCTION ................................................................. 95 The problem, p. 95; advantages of Arcella for genetic studies, p. 96; characters studied, p. 97; cultural methods, p. 97; fission in Arcella, p. gg parent and offspring, p. gg; counting generations, p. 100; preservation of specimens, p. IOI ; length of life and number of progeny, p. 101 ; computations, p. 102. Variations in spine number and diameter of shell in a “wild” population. ....... 102 Heredity and variation in spine number in families derived from single specimens by vegetative reproduction ............................................. 105 Permanent diversities in spine number among the descendants of a single specimen pmduced by vegetative reproduction ................................... 10g Data before selection was begun, p. I I I ; first selection period, p. 112; second selection period, p. 114; third selection period, p. 115; fourth selection period, p. 115; fifth selection period, p. 116; sixth selection period, p. 117; conclusion, p. 119; non-selection periods, p. 1z0; selection within the high line, p. 122; selection within the low line, p. 123. Permanent diversities in diameter of shell among the descendants of a single speci-* men produced by vegetative reproduction .............................. 124 a. Diversities in diameter of shell between the high and low lines of family 58 124 b. Diversities in diameter of shell between the high and low branches of the low line of family 5 8 . . ................................................. 126 Diversities in diameter of shell and in spine number due to sudden large variations (“mutations”) 127 Branch EF, p. 127; branch E421, p. 129; branch EM, p 129; branch ED, p. 132. Empty shells .................................................................. 139 DISCUSSION .................................................................... 142 SUMMARY 148 LITERATURE CITED 150 ...................................................