Throwing herself on her side, the captive lady shows her appreciation, and by sundry queer contortions declares herself his true and devoted spouse. Then the twain return to the nest, into which the female at once betakes herself, and therein deposits her eggs, emerging when the operation is completed by the opposite hole. During the time she is in the nest (about six minutes) the male swims round and round, butts and rubs his nose against it, and altogether appears to be in a state of defiant excitement. On the female leaving he immediately enters, deposits the milt on the eggs, taking his departure through the backdoor. So far, his conduct is strictly proper, but, I am afraid, morality in stickleback society is of rather a lax order. No sooner has this lady, his first love, taken her departure, than he at once seeks another, introduces her as he did the first, and so on wife after wife, until the nest is filled with eggs, layer upon layer—milt being carefully deposited betwixt each stratum of ova. As it is necessary there should be two holes, by which ingress and egress can be readily accomplished, so it is equally essential in another point of view. To fertilise fish-eggs, running water is the first necessity; and as the holes are invariably placed in the direction of the current, a steady stream of water is thus directed over them. For six weeks (and sometimes a few days more) the papa keeps untiring sentry over his treasure, and a hard time he has of it too: enemies of all sorts, even the females of his own species, having a weakness for new-laid eggs, hover round his brimming nest, and battles are of hourly occurrence; for he defies them all, even to predatory water-beetles, that, despite their horny armour, often get a fatal lance-wound from the furious fish. Then he has to turn the eggs, and expose the under ones to the running water: and even when the progeny make their appearance, his domestic duties are far from ended, for it is said (although I have never seen him do it), ‘When one of the young fish shows any disposition to wander from the nest, he darts after it, seizes it in his mouth, and brings it back again.’ There are three species that come into the fresh-waters of British Columbia, to nest and to hatch their young:— _Gasterosteus serratus_, the Saw-finned Stickleback (Ayres, Proc. Cal. Acad. Nat. Sc. 1855 p. 47).—_Sp. Ch._: Body entirely plated; peduncle of tail keeled; the three dorsal spines conspicuously serrated on their edges; anterior fin a little in advance of the base of the pectoral; insertion of ventrals in advance of the second dorsal spine—their own spines serrated on both edges; posterior margin of caudal somewhat hollowed. The colour of the freshly-caught fish is greyish-olive along the dorsal line; but on the sides, particularly in the male, it shades away into an iridescence, like that seen on mother-o’pearl, again changing to pure silvery-white on the abdomen.