NATURE 



[June 20, 19 18 



cyst; the non-formative is the trophoblastic layer. 

 In the Monodelphia, on the other hand, as is well 

 known, the formative cells always form an inner cell- 

 mass enclosed by the trophoblast. The Ornithodelphia 

 (Monotremata) agree with the marsupials in the ar- 

 rangement of the formative and non-formative areas, 

 and for the condition exhibited by these two groups 

 Prof. Hill suggests the term " Phanerotypy," the term 

 " Crvpto'typy " being proposed for the condition met 

 with in the higher mammals. ' Precision in termino- 

 logy is much to be desired, and in this connection we 

 may perhaps point out, without being hypercritical, 

 that the author speaks of four-celled and eight-celled 

 eggs. Surely such stages can scarcely be called eggs. 

 Why not call them embryos? 



There is no fact with which medical men are more 

 familiar than that the nerve-tracts which connect the 

 brain and body are crossed, the right half of the body 

 being united to the left hemisphere of the cerebrum and 

 the left half to the right hemisphere. In 1907 Prof. 

 A. Franqis Dixon, Trinity College, Dublin, sought to 

 explain the crossed arrangement by supposing that 

 it was a result of the primary connection between the 

 right halves of the retinae with the right hemisphere 

 of the cerebrum. The right halves of the retinae 

 receive rays coming from the left field of vision — the 

 field in which the left half of the body is situated. 

 Prof. Dixon pointed out that there is a manifest func- 

 tional advantage in having fhe part of the brain which 

 controls the movements of a limb situated near the 

 cerebral area which receives the visual field in which 

 the limb is situated. To secure that end, the nerve- 

 paths have to be crossed, so that the hemisphere which 

 receives the left visual field will also control the left 

 half of the body. In the Dublin Journal of Medical 

 Science (March, 191S) Prof. Dixon has carried his ex- 

 planation a stage further — an extension due to the 

 discovery by Col. W. T. Lister and Lt.^ol. Gordon 

 Holmes that the retinal picture is inverted in the 

 visual cortex of the brain, the upper half of the field 

 of vision falling on the lower half of the visual cortex. 

 It is well known that the movements of th^ body are 

 represented in an inverted order in the cortex of the 

 brain, those for the mouth and face being placed 

 lowest down, and those for the lower limb higher 

 up. If the retinal connections are the circumstances 

 which determine the distribution of cortical areas, 

 as Prof. Dixon supposes, the visual fields being 

 inverted in the cortex of the occipital lobes, then we 

 should expect, just as we actually find to be the case, 

 a corresponding inversion of the motor areas — the 

 movements of those parts of the body which lie in 

 the upper field of vision being lowest down on- the 

 surface of the brain, and those in the lower visual field 

 highest up. 



The American fuel famine is discussed at length, in 

 the American Museum Journal for February, by Prof. 

 C. Berkey and Mr. C. van Hise. The shortage of 

 coal, which is acute, and has demanded drastic legisla- 

 tion, is in no way due, they remark, to any 'pre- 

 cautionary measures engendered by fear of exhaust- 

 ing the mines, for careful estimates show that at the 

 piesent rate of consumption, which is enormous, the 

 mines of the United States will continue to vield for 

 something like two thousand years. The scarcity is 

 to be attributed entirely to the unprecedented demands 

 to feed the multifarious industries dependent upon 

 coal and the difficulties of transport. Labour and 

 distribution, in short, are unable to keep pace with 

 the deniand. But Prof. Berkey is of opinion that the 

 anthracite reserves are being depleted at a much 

 faster rate than the bituminous coals, and will prob- 

 NO. 2538, VOL. lOl] 



ably not last more than a hundred years. The rate 

 of production of bituminous coals at the present time 

 in the United States is about 600,000,000 tons per 

 annum. 



The problems in the development of British Guiana, 

 a somewhat neglected Possession, are discussed by 

 Sir Walter Egerton in the Journal of the Royal 

 Society of Arts foc- May 31 and June 7 (vol. Ixvi., 

 Nos. 3419 and 3420). Sanitation, drainage schemes, 

 and improvement of the water supply are all required. 

 These, as well as administrative reforms, are discussed 

 by Sir Walter Egerton, but he lays most stress on 

 questions of population and communication. Nearly 

 50 per cent, of the inhabitants are East Indians, and 

 their numbers are increasing. The prosperity of the 

 sugar industry rests on their labours. Chinese used 

 to come in large numbers many years ago, and proved 

 most useful, but the Chinese population is now small. 

 Sir Walter Egerton insists that interference with the 

 immigration of East Indian and Chinese of both sexes 

 in equal numbers will prevent the due development of 

 the colony. At present the cultivated area of British 

 Guiana is more or less confined to a coastal strip of 

 plains intersected with drainage and irrigation canals. 

 This gives little scope for an increased white popula- 

 tion. . The interior ot the colony, however, is largely 

 rich savannah land, more healthy than the coast, and 

 well adapted for cattle-ranching. There are also great 

 possibilities in gold and diamond mining. These con- 

 siderations emphasise the second great need of the 

 colony — railway communication with the interior by a 

 line from Georgetown to Rupununi savanna and the 

 Brazilian frontier. At present the only route to the 

 interior Is by water, and It is not easy. 



The May issue (vol. il., No. 5) of the quarterly 

 Journal of the Society of Glass Technology contains 

 an important article by Prof. Boswell on British sup- 

 plies of potash-felspar. A good account is given of 

 all the more important localities where potash felspar, 

 orthoclase or microcllne, is known to occur in quanti- 

 ties sufliiclent to warrant the assumption that it may 

 prove to be of economic Importance, the questions of 

 purity of the material, quantity available, ease of 

 access, and convenience of transport being all con- 

 sidered. The author holds definitely that felspar 

 from all the known British localities requires to be 

 hand-picked in order to obtain it in a state of 

 purity sufficient to enable it to be used in glass or 

 pottery manufacture or for the extraction of potash. 

 There are practically seven groups of localities repre- 

 sented, namely, (i) Cornwall, (2) bet-ween Lochs Lax- 

 ford and Inchard, (3) between Durness and Eireboll, 

 (4) near Overscalg, Loch Shin, all the three last- 

 named being situated in Sutherlandshire, (5) Belleek, 

 on the borders of Co. Donegal and Co. Fermanagh, 

 (6) Glenties, in Co. Donegal, and (7) Belmullet, in 

 Co. Mayo. It would appear that the purest felspars 

 are those of Cornwall and Belleek, the deposits being 

 in both cases fairly accessible, but the quantities In 

 both places appear to be limited. The other localities 

 show much larger quantities of mineral, but their 

 potash contents are decidedly lower, and the localities 

 are for the most part inconveniently situated in respect 

 of transport. The author does not appear to think 

 that, as a source of potash, any of these felspar 

 deposits Is likely to be economically workable ^ in 

 normal times, but is apparently rather more sanguine 

 as to the prospects of the best of these deposits^ as a 

 source of supply to the glass and pottery industries. 



G. Vallauri, in Elettrotecnica for January 25 and 

 February 5 .last, discusses at some length the theory 



