Cuap. I. FECUNDATION. 491 
every succeeding year there appears in that organ a larger and larger set of eggs, 
each set made up of the usual average number of eggs which this species lays, so 
that specimens eleven years old, for the first time, contain mature eggs, ready to 
be laid in the spring. 
Now another question arose, When are the eggs fecundated? Field observa- 
tions soon taught me that this species copulates before it is eleven years old; I 
have even seen those that were not over seven years old already performing the 
act, though I have never seen any in copulation younger than these. Thus it 
appears that the first copulation coincides with a new development of the eggs, 
in consequence of which, a certain number of them, equal to that which the spe- 
cies lays, acquire a larger size, and go on growing for four successive years before 
they are laid, whilst a new set is started every year, at the period of copulation 
in the spring, enabling this species to lay annually from five to seven eggs, after 
it has reached its eleventh year. 
The question was then naturally suggested, whether fecundation is the result of 
the first act of copulation, or of the second, the third, or the last; or whether 
the first copulation only determines the further growth of a certain number of 
eggs, which require a series of successive fecundations to undergo their final devel- 
opment. The second alternative appears the more probable when it is remem- 
bered that Turtles were observed! which did not lay their eggs as usual, though 
the yolk had undergone all the regular changes through which it passes, up to 
the time the egg has entered the oviducts. This is another fact which tends to 
prove that fecundation is a successive act. Though Turtles lay only once every 
year, soon after the period of copulation in the. spring, copulation itself does not 
take place once merely, every year, as in all the animals known to bring forth 
young once annually; it is repeated a second time, every year, m the autumn, 
* and this takes place 
shortly before the Turtles retire to their winter-quarters ; 
without apparent connection with any marked change in the growth of the egy 
at that season. So, in Turtles, fecundation does not appear to be an instanta- 
neous act, resulting from one successful connection of the sexes, as it is with 
most animals. The facts related above show, on the contrary, that, in Turtles, a 
repetition of the act, twice every year, for four successive years, is necessary to 
determine the final development of a new individual, which may be accomplished 
in other animals by a single copulation. 
It may be suggested, that, by an investigation of the spermatic particles, addi- 
tional light would be thrown upon these remarkable circumstances. But such 
investigations present greater difficulties in these animals than could be supposed 
1 See below, Ch. 2, Sect. 4. 2 Comp. Part II., Ch. 1, Sect. 11, p. 284. 
