Page:Science vol. 5.djvu/281

 Maucs S7, 188S.)

��I, anil hraviiip, in cousin que lire of Ihe severe frodU In tiAiTow gorges tbU nction had the effect of •epATkllng Ihe boirlders from Uie day, anil throwing tbem lo the centre into rows so regular as to suggest design. Hansfield Island is tow, slid, from dUinte- grsttoQ of the rocks, looks like one gigantic ridge of gravel. Uie solid rock showing through ibe dihria nnly at interviU. The formation is of gray limestone, in Ihin horiioiital terraced beds, contnlning fossils, probahly Silurian. Southampton Island is very simi- lar, but appears to support a little more vegetation. Al Harbie tslanil, dlorltes and schists of the Huronian series are found; and the island probably derives its name from the while anil light-colored qtiartziles of which the whole of the western part consists, and whicb bear a strong resemblance to while and veined marble. The surfiices of the beds are often strongly rippte-markod.

In considering the glaciation of the district, Dr. Bell remarks, that, if the sea here were only a hun- dr^ tatboms lower than at present, James and Hud- son bays would be a plain of dry land, more level in pmportinn to Its extent than any other on Ihe conll- nenL The numerous rivers that flow into it would traverse this plain, after having converged into one immeDse river towards ihe eaulern limit of Ihe pla^ leau. and would empty into the strait near DIgges, the strait remaining as a large bay, very much in its present shape.

During the 'great ice age,' the baalu of Hudson Bay may have formed a sort of glacial reservoir, receiving stroains of ice from the east, north, and nortb-west, and giving forth the accumulated result as broad glaciers, mainly towards the south and south- west. In the strait, the direction of the well-marked glaciation is invariably eastward; and the composi- tion of the drift, which includes Huronian limestone fragments similar to the more westerly formations. as well as the long depression of Fox's Channel and the strait, deepening as it stretches eastward, all point to the passage of an extensive glacier Inlo the Atlantic. This glacier was probably joined by part of that occupying the site of Hudson Bay, and by another, also from the southward, coming down the ralley of the Koksok River and Ungava Bay; these united streams still moving eastward, round Cape Cbudteigb, into the ocean.

Throughout the drift-period, the coast-range of Labrador held its head above the Ice, especially the hif^ northern part; but, In going south, giaciiil action seems to have reached a height of n thousand feet at least. Here the course followed by the ice is down the valleys and fiords directly into the sea; while, on the Island of Newfoundland, It appears to have been Irom Ihe centre towards the sea, on all sides.

��BIOLOGICAL NOTES.

Okk of the principal distinctions between the

mammalia and the lower vertebrata has been hitherto

supposed to he the possession by the former of a

��placenta. Duval, however (Voiirii. iiiuit. phyai"!., 1884, Iil3), has come to the conclusion that it also exists, though in a rudimeuiary form, in birds. The allantois, passing Inward into the pi euro-peritoneal cavity, does not become attached lo the amnion or the umbilical vesicle, but joins the chorion, becom- ing fused with it. It ends by forming a sac, which encloses amass of albumen; and inlolhissacthe villi of the chorion project, forming an oi^an completely anali^ouB lo the placenta of the mammalia. There is recessarily a difference in the form of this organ, due to the different modes of reproduction; in mam- mals the villi of the chorion being attached to the mother, while In birds they must attach themselves to the nutritive albumen. It is, however, quite In- telligible, Ibat In an ovovivlparous vertebrale, where the egg lias a thin membranous shell, the placentold organ should become attached to the Internal surface of the oviduct. This placenta of birds Is therefore a rudimentary oi^an which enables us to understand how the placenta of the mammalia may have orlgl-

For over sixty years Omithorhynchus, or the duck- billed Platypus, has been believed to be oviporous; hut up to the present time the evidence has not seemed to naturalists aufficieni to settle this point beyond a doubt. In JS^itt GeoffroySl. Hilaire, in a communication upon the subject, described the eggs as being of a regular oblong spheroidal form, of equal size at both ends, and measuring an inch and three-eighth i In length and six-ei^tlis of an inch in breadth. It seems now to l>e es- tablished, that these eggi, two in number, are laid at Ihe end of a burrow In the river-bank, about twelve yards from thewater. Theovumofmonotremesbears a close resemblance to that of a saumpsidon, and is very different from that of a true mammal, in that It lias a good-sixed yelk with which the young is nour- ished. It is interesting to observe that the yelk-sac and the umbilical vesicle are really homologous. In monotremes we And, as it were, intermediate animals possessing the attributes of two classes: for, on the one hand, they have developed mammary glands, the distinctive feature of the higher group ; on the other, they lack that structure whereby the typical inara- maiian embryo receives nourishment before birth ; and, in correlation with this, we Gnd them agreeing with the lower cia'S in the jxissefsion of a yelk-sac, whilst the contained food-yelk causes the ovum lo as- sume Ihe meroblasllc type. We may thus trace the line of descent through the Sauropsida, directly to the monotremes (doubtless through forms e:<Linct, as the Theromorpba of Cope}; from these to mar- supials, which are viviparous, but whose ova still possess a large yelk-sac, and whose embryos enter into no close vascular connection with the maternal tissues; and from these to the higher mammals.

In some experiments upon thedigesiion of sponges, von Lendenfeld kept some Australian Aplysinldae in

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