218 THE ZOOLOGIST. 



following actions (which I have actually seen) are explicable on 

 the hypothesis here indicated, viz. : — (1) The nervously excited 

 seizing of things from the ground, and letting them drop again, 

 by the male bird whilst in a state of sexual frenzy, on account 

 of the female, during the courting period. (2) The taking up 

 and playing with materials similar to those of which the nest 

 is composed, by both the male and female bird, immediately 

 followed either by a visit to the nest and coition upon it, or by a 

 start in that direction, with every appearance of there being the 

 same intention, even though it may not be carried out (3) The 

 further association of these instincts — coition, namely, and 

 nidification — at the nest itself. In some of these cases the 

 addition to or manipulation of the material composing the nest, 

 by the female bird, is immediately followed by the invitatory 

 attitude on her part, and as instantly follows the act of coition 

 upon it. The male also joins in these nidificatory acts, both 

 before and after the rite, so that the two forms of activity seem 

 to be united in the birds' minds, and to make together the 

 purpose of their visit. In other instances the female alone acts 

 thus, after coition only. (4) The taking up and again letting 

 fall by the female of the materials of the nest, whilst actually 

 in coitu upon it, so that here we see the two things, as it were, 

 in combination. (5) Habitual coition on the nest, commencing 

 from a period when this word can only be used in relation to 

 place and not structure, and continuing certainly up to the 

 laying of the first egg, and probably afterwards. (6) The 

 remaining of the female on the nest, after coition has taken 

 place there, for an indefinite period, during which the act is 

 repeated. This last, I think, is an important point in my 

 theory, for if it now be asked why the female should remain, for 

 any time, upon a spot or structure which afterwards becomes 

 the nest, for any other reason than such as is connected with the 

 eggs or with nidification, it can be answered that she does so in 

 expectation of the return of the male, and consequent repetition 

 of the act of coition. This helps us greatly in understanding 

 how any place that has once, if only by chance, been made use 

 of for this purpose, might become a more or less permanent 

 pairing-place, through the female bird waiting on upon it, in 

 which case the eggs would sometimes be laid there ; and since 



