Dublin Natural History Society. 3527 



year, and the substance of which I now hasten to lay before you. Into the question 

 of whether this be a distinct species, or merely a well-marked variety of Gasterosteus 

 aculeatus of Bloch, it is not my intention to enter. Suffice it for us to consider it as a 

 distinct species, the smooth-tailed stickleback, the G. leiurus of Valenciennes and Cu- 

 vier. It is the only species I have been able to detect about Dublin, where it abounds 

 in prodigious numbers. When about to spawn, the fish select a suitable spot for the 

 foundation of their nidus, preferring a gravelly bottom, not too deep, and over which a 

 current runs ; hence the best place to look for the nests is where clear streams empty 

 themselves into a river. At such a place you will almost invariably find abundance of 

 them in the months of May, June and July. Another favourite locality is a large flat 

 stone at the bottom of the river, over the edge of which the water flows, so as to pro- 

 duce a ripple. Having chosen a suitable spot, he (for it is always the male that builds) 

 begins by laying a foundation. This is slightly modified, according to the materials 

 of which the superstructure is to be made. If, as is most usually the case, of straws 

 and such like, the first thing done is to lay a number of these on the bed of the stream, 

 carefully tucking the ends of them down into the gravel upon which they rest ; across 

 these are laid other straws, the ends of which are either interlaced amongst the first 

 row, or tucked into the gravel. This last operation is always performed by means of 

 the animal's snout, the point of which he places on the end of the straw, &c, and then 

 raising the body perpendicularly, he thus presses the straw or other material among 

 the stones or mud. Amongst and over these straws Confervas and such like are inter- 

 woven, rendering the whole one compact mass, through which the water, however, can 

 have free passage. He always takes care to preserve a dome-like hollow in the centre, 

 in the top of which there is a small round hole ; the edges of this he takes particular 

 care to strengthen, tucking in the straws and rounding off the edges most industrious- 

 ly ; and every now and again he pauses in his task, and remains hovering over the 

 nest, as though trying by the current produced by the motion of his fins whether the 

 structure is secure enough or not. Sometimes the nest is entirely made up of fresh- 

 water Algae, and in this case the foundation is a most beautiful object, being as circu- 

 lar as though marked out with a pair of compasses. I have also seen it composed 

 almost entirely of decayed leaves of trees ; this was in a muddy ditch, and the nest was 

 a most untidy-looking affair. Whatever materials he uses, he always takes care to 

 preserve the hole in the centre, boring at it every now and then with his snout for five 

 minutes at a time. It is most interesting to watch the little architect at his labours ; 

 one while with a straw or piece of stick in his mouth, three or four times as long as 

 himself, or else carrying a bunch of Conferva?, in which his head is nearly completely 

 concealed ; at another while, either hovering over the nest or boring at it with his snout, 

 or else attacking some audacious intruder who has dared to trespass on his domain — 

 for I believe it is well known that these fishes always select a spot for themselves, over 

 which they keep guard with the greatest jealousy. One morning I was much enter- 

 tained by a contest of this kind. Two fish had selected a large flag, of about two feet 

 square, as the foundation for their nests. Every minute or two, either in procuring 

 straws, or in returning with them, they would come in contact; then there would be a 

 rush at each other, and in a minute or two, the weaker fish having given way, there 

 would be a chase for two or three minutes, during all which time the fishes never drop- 

 ped the straws; the conqueror invariably returning in triumph, and sailing proudly 

 two or three times round his nest. They seem to have some judgment in the selection 

 of their materials, as I have often observed a fish, after carrying a straw for some dis- 



