SCIENCE 



257 



traction, and heaving, in consequence of the severe 

 frost. In narrow gorges this action had the effect of 

 separating the bowlders from the clay, and throwing 

 them to the centre into rows so regular as to suggest 

 design. Mansfield Island is low, and, from disinte- 

 gration of the rocks, looks like one gigantic ridge of 

 gravel, the solid rock showing through the debris only 

 at intervals. The formation is of gray limestone, 

 in thin horizontal terraced beds, containing fossils, 

 probably Silurian. Southampton Island is very simi- 

 lar, but appears to support a little more vegetation. 

 At Marble Island, diorites and schists of the Huronian 

 series are found ; and the island probably derives its 

 name from the white and light-colored quartzites of 

 which the whole of the western part consists, and 

 which bear a strong resemblance to white and veined 

 marble. The surfaces of the beds are often strongly 

 ripple-marked. 



In considering the glaciation of the district, Dr. 

 Bell remarks, that, if the sea here were only a hun- 

 dred fathoms lower than at present, James and Hud- 

 son bays would be a plain of dry land, more level in 

 proportion to its extent than any other on the conti- 

 nent. The numerous rivers that flow into it would 

 traverse this plain, after having converged into one 

 immense river towards the eastern limit of the pla- 

 teau, 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 basin of Hudson 

 Bay may have formed a sort of glacial reservoir, 

 receiving streams of ice from the east, north, and 

 north-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 into 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 

 valley of the Koksok River and UngavaBay; these 

 united streams still moving eastward, round Cape 

 Chudleigh, into the ocean. 



Throughout the drift-period, the coast-range of 

 Labrador held its head above the ice, especially the 

 high northern part; but, in going south, glacial action 

 seems to have reached a height of a 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 

 from the centre towards the sea, on all sides. 



BIOLOGICAL NOTES. 



One of the principal distinctions between the 

 mammalia and the lower vertebrata has been hitherto 

 supposed to be the possession by the former of a 



placenta. Duval, however (Joiirn. anat. physiol, 

 1884, 193), has come to the conclusion that it also 

 exists, though in a rudimentary form, in birds. The 

 allantois, passing inward into the pleuro-peritoneal 

 cavity, does not become attached to the amnion or 

 the umbilical vesicle, but joins the chorion, becom- 

 ing fused with it. It ends by forming a sac, which 

 encloses a mass of albumen; and into this sac the villi 

 of the chorion project, forming an organ completely 

 analogous to the placenta of the mammalia. There 

 is necessarily 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, that in an ovoviviparous vertebrate, where 

 the egg has a thin membranous shell, the placentoid 

 organ should become attached to the internal surface 

 of the oviduct. This placenta of birds is therefore 

 a rudimentary organ which enables us to understand 

 how the placenta of the mammalia may have origi- 

 nated. 



For over sixty years Ornithorhynchus, or the duck- 

 billed Platypus, has been believed to be oviparous; 

 but up to the present time the evidence has not 

 seemed to naturalists sufficient to settle this point 

 beyond a doubt. In 1829 Geoffroy St. 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-eighths 

 in length and six-eighths 

 of an inch in breadth. 

 It seems now to be es- 

 tablished, that these eggs, two in number, are laid at 

 the end of a burrow in the river-bank,, about twelve 

 yards from the water. The ovum of monotremes bears 

 a close resemblance to that of a sauropsidan, and is 

 very different from that of a true mammal, in that it 

 has a good-sized 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 find, 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 mam- 

 malian embryo receives nourishment before birth; 

 and, in correlation with this, we find them agreeing 

 with the lower class in the possession of a yelk-sac, 

 whilst the contained food-yelk causes the ovum to as- 

 sume the meroblastic type. We may thus trace the 

 line of descent through the Sauropsida, directly to- 

 the monotremes (doubtless through forms extinct, 

 as the Theromorpha 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 the digestion of sponges, 

 von Lendenfeld kept some Australian Aplysinidae in 



