LIFE CYCLE OF HYDATINA SENTA 295 
TABLE 4 
Showing number of male- and female-producers in two lines of Hydatina senta, one 
line being derived from the other by inbreeding, as in table 2 
| 
LINE A | INBRED LINE 
mate of rst Number of o) Number of 2 9| Date of first Number of o'9| Number of ? 2 
young | | young | 
June | October | 
17 7 14 12 35 16 
19 11 | 17 | 14 | 23 25 
21 20 22 | LG 0 21 
22 25 | 11 i 18 33 16 
23 25 | 24 } 20 | 1 11 
25 1900" 9 | | 30 22 
26 21 | 14 | 22 | 43 8 
27 29 19 | 27 | 0 16 
| | 29 23 14 
eee. = | } | — 
ALO Gall terate'a's 157 130 | | 188 149 
: az =m |p I 
Per cent of | 
Sot ee 54.7 | B57 
4 was derived from a female taken from a culture in the labora- 
tory about June 1. This culture originated from a collection of 
rotifers taken at Grantwood, New Jersey, in the latter part of 
March, 1911, and transplanted to manure cultures in Ann Arbor 
shortly afterwards. These manure cultures were maintained 
without observation until June, when the female that became the 
parent of line A was isolated. 
Females of line A were paired with males of the same line about 
June 25 to June 27, and fertilized eggs obtained. These eggs 
were allowed to dry in the dishes and to remain dry until the last 
of August, when they were again covered with water. Females 
began to hatch from them in a week, and from one of them the 
‘inbred line’ of table 4 was started. Completed records of this 
line were not kept until October 12, after which date eight com- 
plete generations were recorded. 
The two lines in table 4 may not be of the same age; either one 
may be the older. Furthermore, since they were not bred simul- 
taneously, the conditions may not have been the same. How- 
