THE CYNIPIDA AFFUCTING THE OAK. 31 
but as years passed investigations made by other 
naturalists (Sars, Siebold, and Lovén) proved that he 
was correct. 
In 1842 J. J. 8. Steenstrup published (‘Uber den 
Generationswechsel’) all that was known on the sub- 
ject. The essay was translated into English by George 
Rusk, and published by the Ray Society, 1845. Steen- 
strup quaintly describes this mode of reproduction as 
“a peculiar form of fostering the young of the lower 
classes of animals.” The preface (loc. cit, p. 1) contains 
the following paragraph: “ Alternation of generations 
is the remarkable, and till now inexplicable, natural 
phenomenon of an animal producing an offspring, 
which at no time resembles its parent, but which, on 
the other hand, itself brings forth a progeny, which 
returns in its form and nature to the parent animal, so 
that the maternal animal does not: meet with its 
resemblance in its own brood, but in its descendants 
of the second, third, or fourth degree or generation.” 
The bi-sexual, therefore, gives rise to the asexual or 
agamic, and the agamic in its turn to the bi-sexual. 
Moreover, the: two generations produce galls which 
differ entirely in shape, size, and situation. 
One generation consists of females only, the other 
includes both males and females, The bi-sexual insect 
is the resul€ of the union of the male and female, the 
agamic when that condition is absent. 
The theories of non-sexual reproduction are very 
complex. The facts, however, are simple. From 
many oak galls which mature in the spring or early 
summer females only emerge, and without assistance 
of the male they lay eggs from which larve hatch. 
This is known as parthenogenesis, a word given to the 
phenomenon by Professor Sir Richard Owen. The 
galls caused by these larve mature in early autumn, and 
from them there issue both male and female imagines, 
from the union of which eggs are deposited, and the 
resultant larve produce galls like their agamic grand- 
parent. The ability to reproduce parthenogenetic eggs 
