a time when the Straits of Dover either did not exist, or were the bed of a river running from the west; and when, as I told you just now, all the rivers which now run into the German Ocean, from the Humber on the west to the Elbe on the east, discharged themselves into the sea between Scotland and Norway, after wandering through a vast lowland, covered with countless herds of mammoth, rhinoceros, gigantic ox, and other mammals now extinct; while the birds, as far as we know; the insects; the fresh-water fish; and even, as my friend Mr. Brady has proved, the Entomostraca of the rivers, were the same in what is now Holland as in what is now our Eastern counties.  I could dwell long on this matter.  I could talk long about how certain species of Lepidoptera—­moths and butterflies—­like Papilio Machaon and P.  Podalirius, swarm through France, reach up to the British Channel, and have not crossed it; with the exception of one colony of Machaon in the Cambridgeshire fens.  I could talk long about a similar phenomenon in the case of our migratory and singing birds:  how many exquisite species—­notably those two glorious songsters, the Orphean Warbler and Hippolais, which delight our ears everywhere on the other side of the Channel—­follow our nightingales, blackcaps, and warblers northward every spring almost to the Straits of Dover:  but dare not cross, simply because they have been, as it were, created since the gulf was opened, and have never learnt from their parents how to fly over it.

In the case of fishes, again, I might say much on the curious fact that the Cyprinidae, or white fish—­carp, &c.—­and their natural enemy, the pike, are indigenous, I believe, only to the rivers, English or continental, on the eastern side of the Straits of Dover; while the rivers on the western side were originally tenanted, like our Hampshire streams, as now, almost entirely by trout, their only Cyprinoid being the minnow—­if it, too, be not an interloper; and I might ask you to consider the bearing of this curious fact on the former junction of England and France.

But I have only time to point out to you a few curious facts with regard to reptiles, which should be specially interesting to a Hampshire bio-geologist.  You know, of course, that in Ireland there are no reptiles, save the little common lizard, Lacerta agilis, and a few frogs on the mountain-tops—­how they got there I cannot conceive.  And you will, of course, guess, and rightly, that the reason of the absence of reptiles is:  that Ireland was parted off from England before the creatures, which certainly spread from southern and warmer climates, had time to get there.  You know, of course, that we have a few reptiles in England.  But you may not be aware that, as soon as you cross the Channel, you find many more species of reptiles than here, as well as those which you find here.  The magnificent green lizard which rattles about like