296 GARY N. CALKINS 
The low vitality of the J series cannot be due to congenital 
weakness of the parent A whose relative vitality was 90.9 per 
cent. Other filial series from this same parent were all more 
vigorous, the C series with relative vitality of 97.7 per cent, 
H series 78.6 per cent, and D series 73.6 per cent, all of which 
came from the parent A series in its period of youth. 
The R series came from the congenitally weak J series, but 
the inherited weakness was enhanced by the advanced age of 
the J series when R was started. The N series with a relative 
vitality of 71.3 per cent came from the same parent J series when 
it was only forty days younger, and the combined effects of 
inherited weakness and age of parents was evident in its own 
vitality. A W series, from N 225, is now living and has lived 
for 229 days without conjugating and with an average division 
rate of only 9.7 divisions in ten days. The low vitality of the a 
series, which was next to the weakest that I have cultivated, 
was probably not due to congenital weakness, for the same parent 
gave rise to the V series with a relative vitality of 88.1 per cent. 
But the V series came off during the period of youth while a 
came off during the period of age. 
The Q series, finally, came from the I series when the latter 
was 200 days and 316 generations old. The same parent with a 
relative vitality of 89 per cent gave rise to the L series with 
vitality of 74.5 per cent. 
With the exception of the N and the R series, both of which 
came from the J series during an advanced age, there is no weak 
ancestor in the heritage of these weak series. The J series came- 
directly from A, the first ancestor of the cultures. The a series 
came from P (95 per cent); P from L (74.5 per cent); L from I 
(89 per cent); I from F (94.1 per cent); F from C (97.7 per cent), 
and C from A (90.9 per cent). The Q series from I has the same 
early and strong ancestry. 
There is evidence, therefore, that these series with extremely 
low relative vitality owe their weakness to the nearly exhausted 
vitality of their parents. Yet, low as their vitality was, they 
all, nevertheless, showed the characteristic rejuvenating effect 
of conjugation as shown in table 8, columns 4 and 5. 
