LIFE CYCLE OF HYDATINA SENTA 307 
yielded a male-producer. It is quite possible that an error was 
made in determining the relative ages of these first individuals, 
for, as stated above, the relative ages of the young rotifers iso- 
lated at one time was determined from their relative sizes. When 
the oldest rotifers were much alike it was sometimes difficult to 
determine relative ages. But in any case, I do not think it is 
possible that I have misplaced this individual by more than one 
step in order of age. That is, the first male-producer in the sec- 
ond family of table 10 can hardly have been later than the second 
young produced after the mother was transferred to spring water. 
TABLE 10 
Showing number, and order of production, of male- and female-producers in seven 
families of Hydatina senta, in which the early eggs were laid and hatched, and the 
young reared to maturity, in manure solution, the later eggs laid and hatched, 
and the young reared to maturity, in spring water 
& 
oe LAID, HATCHED AND REARED IN MANURE LAID, HATCHED, AND REARED IN SPRING 
ga SOLUTION WATER 
a 
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| fe) omen Oooo 
2at\\ PPO QVPPQPASPPVIMSF SLAP APH AAA PLL PLL LAE 
| 229229999 
3 Lo) May toyster" {oo} ey (0) Con Koy fo Lolaony Konmon to (fe) (0)"(9) (2) 
4 POP PPP ViPVPVPVPVVPVSVPeVeePeee 
5 POPOV OVOP SPQVVPMIPRAP PLASM LAH APPL AAGA EP 
6 PO QPVPWPPMPAPAVPOPVPVPAMHP MSG ASPLRASPASP SPS APAS LLP LP ASL LAA 
OO OVORO OOF OTO O IOE OF ONS 
uf POO QPPWPHPRPAVPWMHSRASPVPMIVPSP ASS SRLPASPSLPSP HS LPL LAA 
| FIPFLAPLPAHPQLPAGIAS LAA 
The average number of eggs laid by these females on the days 
when they were transferred to spring water was 14.4 per day. 
That is, an interval of 1.66 hours elapsed between the laying of 
two successive eggs. Since the first male-producer in the second 
family in table 10 was not later than the second one produced 
after its mother was transferred to spring water, the nature of 
this female was not determined until within 2 x 1.66 hours, or 
3.32 hours, before laying. 
