LIFE CYCLE OF HYDATINA SENTA 285 
TABLE 1 
Showing proportion of male-producers in eight parthenogenetic lines of Hydatina 
senta in successive generations. The generations are taken two by two, and the 
proportions are given in per cents. 
| GENERATION 
ESTO: eh ae an Oe 42.2| 49.1) 66.2. 7 | 
5.9 | 64.0 | 31.8) 5.1) 47.4| 77.3 | 64.2 | 36.4 | 18.9 
Ware Derg ors esc cl 19.1) 12.5 | 28.1| 0.0 26.4 | 62.5 | 25.4 | 79.2| 20.4/ 4.4) 0.0] 32.2 
LONI Wp eg nea eee 60.0 | 69.5 | 50.0 | 48.7| 6.8 | 42.1 | 12.2] 30.3] 33.8| 0.0| 42.3 | 36.3 
ee Ans 22, 11.2| 27.4] 1.7] 1.4) 27.8| 9.5] 7.1| 7.0] 5.0) 8.7 | 45,5 | 10.3 
Rime ol aoc tac onacese ee 45.2 | 29.8 | 47.0 | 25.4 | 54.2 | 53.2 | 49.4 | 33.3 | 37.2 | 34.8| 9.0| 48.7 
sine een. a tee taee se: 0.0| 4.0] 0.0| 1.1/| 10.2) 35.4] 0.0) 0.0) 0.0/ 17.6) 4.9) 2.9 
MING (etek ee en ed AB, Oh Or O)|e 2D || 12,1, °2%0) | 45-85 eee ovede | tsa) ONGy) 169 
ine gee wees. hole 31.3 | 56.1 | 33.6| 15.8] 9.2] 11.6] 0.0] 7.8] 14.2] 18.6] 1.6] 8.7 
AVeriBe 5 Sette Tero 26.3 | 33.4 | 28.3 | 21.3 | 25.0 | 31.0 | 18.1} 26.0 | 26.9 | 18.7 | 18.7 | 20.0 
GENERATION 
25-26 | 27-28 29-30 31-32) 33-34, 35-36) 37-38 39-40 41-42) 43-44 45-46 
5] 0.0} 2.5] 8.4] 6.8] 3.4] 0.0) 9.5| 48.5 | 26.3) 66.2 
IO: Saks eae eee oa eS 17.5 | 52.3 | 17.5 | 14.9 | 25.3 | 12.0] 4.5|/15.3] 5.5) 0.0| 4.6 
DTS SANE 5 See See a ene ee 34.0 | 42.8 | 24.4 | 23.8 | 45.5 | 40.6 | 32.3 | 38.9 | 34.4 | 50.0) 3.4 
TPs WL Ni ay ts sa ata 27.9 | 58.9] 43.0 | 62.6 | 13.0] 16.3] 17.6] 15.1] 3.3] 17.0) 2.6 
Mine Seep ee mbes ecek sear tt 29.0| 19.3 0.0) 13.3 | 40.8 | 18.4 | 22.9 | 43.1 | 16.2 | 10.9 | 25.0 
TEATS Ge Gaeta peace: 11.8 | 22.4] 13.6| 5.4] 14.2] 17.8] 0.0] 5.0) 23.4) 8.0} 3.4 
Let 7 ee oe ee 52.0| 10.2} 0.0] 9.6] 6.6] 31.5] 0.0] 0.0] 1.5] 0.0} 0.0 
Lit Cae, Been eae aces ee 16.9 10.6 | 25.0 4.2 | 34.1 1.71 2.9) erase 1215 |020))) 050 
. | | | | | 
ISAS ae oR Ge Atenas | 24.2 | 26.4 | 15.8 | 17.8 | 23.8 | 17.7} 10.0 | 16.8 | 18.1 | 14.0 | 13.2 | 
In compiling the data, I have combined the generations two 
by two, partly to save labor in computing percentages, partly 
to smooth out the great fluctuations that often occur from one 
generation to the next. Two methods of handling the data would 
have been practicable. All the male-producers and the female- 
producers, respectively, of corresponding generations in all eight 
lines could be added together, and the percentage of male-pro- 
ducers computed for the whole group. Or the percentages could 
be determined for each line separately, and then an average of 
the eight percentages in corresponding generations computed. 
The former method would give to a line producing large families 
much greater weight in determining the end result than to a line 
that produced small families; the latter method makes all the 
lines of equal importance, regardless of the number of individuals. 
