630 
GILBERT E. JOHNSON. 
the fact that, although only those females which were placed 
with males reproduced, yet by no means all, but only a small 
percentage of them, did so. 
Culture D. — Several nephridia, with the nematodes which 
they contained, were removed wholesale from a freshly killed 
Lumb. terrestris. Fourteen of the larvm were picked out 
and isolated in watch-glasses with worm extract. All but 
three died while larval, before their sex was indicated. (I 
represent such individuals in the culture-table by a plain circle. 
Of the three survivors two developed into females and one into 
a male. The one female, which I shall call A, began to lay 
disintegrating eggs. (Disintegration is a sign that the egg has 
not been fertilised.) The male was put with the other female, 
B, which had not yet laid any eggs at all. Next day B 
began to lay fertilised eggs, from which larvm (F^ generation) 
hatched out. The male was then removed from B and placed 
with A, which had by this time ceased to lay even sterile eggs. 
Two days later A also began to lay fertilised eggs, from 
which larvae (Fi generation) hatched out. 
Eight larvae were isolated from among the offspring of B. 
All developed into females. So did all the unisolated larvae 
of the same brood and also A’s brood. None of the 
eight isolated females reproduced, even though extraneous 
males, taken from a culture of the nephridial form reared on 
decaying nephridia, were placed with two of them. Nor did 
the unisolated females of A’s or B’s broods reproduce. 
Table 2.— Culture D. 
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