1068 REPORT—1885. 
differentiation between those of the outer and inner seas, resulting, as we have seen, 
in almost an entire specific change, was effected. 
The above view seems in accordance with recent observations regarding the 
adaptability of many marine forms to new lacustrine conditions, provided the pro- 
cess of change is sufficiently gradual. Professor Sollas, whose memoir on ‘ The 
Origin of Fresh-water Faunas ’? is very suggestive, arrives at the conclusion that, as 
the conversion of comparatively shallow continental seas into fresh-water lakes has 
taken place on a large scale several times in the history of the earth, this has been 
accompanied by the transformation of some of the marine into fresh-water forms. 
The Jordan valley lake, originally salt, has shrunk back into two or three lakes 
connected by a river. The Dead Sea alone remains salt and lifeless. The waters 
of the Sea of Galilee are fresh, and teem with life. In reply to my inquiry 
whether the above views would harmonise with his own, Professor Sollas writes : 
‘I have always regarded the curious fishes of the Sea of Galilee as evidence of a 
previous marine communication, but it never occurred to me to speculate as to the 
age of that connection. If this sea (that of Galilee) were stocked from the Eocene 
ocean it would fit in very well with the history, as I believe it, of other fresh-water 
faunas.’ It is gratifying to me to have the concurrence on this point of so able an 
authority. 1 conclude, therefore, that the special forms of fishes now inhabiting the 
Sea of Galilee are the descendants of those which lived in the Eocene ocean. 
6. On the Cause of the Rutreme Dissimilarity of the Faunas of the Red Sea 
and Mediterranean. By Professor Epwarp Hutt, LL.D., F.RB.S. 
The author pointed out that the faunas of these seas haye descended from the 
forms which lived in the Eocene Ocean. In the succeeding Miocene epoch, when 
the lands rose from the waters, the Mediterranean area was cut off from that of the 
Red Sea, and as different conditions would be thus brought about, especially in the 
ease of temperature, the faunas would develop independently in both seas. This 
process of development and differentiation went on throughout the Miocene 
period and down into the Pliocene, when the lands were again submerged to a 
depth of 220 to 250 feet, and a connection of the two seas was re-established. 
But the depth of water over the connecting strait not being greater at its minimum 
than about 200 feet, although allowing a commingling of the littoral and shaliow 
water forms, would have been insufficient to bring about a general community of 
species, especially those inhabiting the deeper waters on both sides, and when the 
land again rose, and the isthmus was established, the forms which had crossed 
from sea to sea would afterwards die out. From this it has resulted that the 
faunas of the Mediterranean and Red Seas are almost entirely dissimilar, only 
18 species, according to Professor Issel, being common. It would be an interesting 
inquiry, which of these faunas more resembles the original Eocene stock. 
7. On the Morphology of the Human Arterial System. 
By Professor A. MacAuister, F.R.S. 
8. On the Viscera of Gymnotus electricus. 
By Professor CLetanp, M.D., F-.R.S. 
Independent of its electric organs, this fish has a number of remarkable internal 
peculiarities. The curious spongy protuberances of the mucous membrane of the 
buccal cavity are well known to zoologists. The two swimming bladders are re- 
markable for their relation to the kidneys; the anterior swimming bladder being a 
small structure between their anterior extremities, and the larger posterior swim- 
ming bladder being situated altogether behind their united hinder ends, while the 
duct of the latter ascends by the left side of the renal outlet, to be joined by the 
) Scientifie Trans. Royal Dublin Society, vol. iii. (ser. I1.). 
