May 25, 1911] 



NATURE 



4'> T 



nurse-cells ; the resting egg arises from a modified group of 

 four cells, which absorbs numerous other four-celled groups. 

 The author confirms Weismann's statements that the 

 origin of resting eggs is not connected with any influence 

 of the male, that these eggs do not enter the brood pouch, 

 but if not fertilised degenerate in the ovary, that the 

 carapace of Daphnia changes into an ephippium only if 

 the ovary is forming resting eggs, and that these eggs 

 invariably give rise to females. 



(6) The Donaciinae, a sub-family of the Chrysomelidse 

 (leaf-beetles), are of special interest on account of certain 

 peculiar features in the habitat and mode of life of the 

 larvje, which are fully described and illustrated in Dr. 

 Boving's memoir, which also contains an exhaustive 

 account of the larval anatomy. The author concludes that 

 the features hitherto utilised to differentiate the larvae of 

 Hsemonia and Donacia are unserviceable ; it has, in fact, 

 not been possible to find real generic distinctions between 

 the larvae, although the adults present well-marked differ- 

 ences. Conversely, though the adults of Donacia and 

 Plateumaris have been found to exhibit only small differ- 

 ences, from which it might have been expected that the 

 larvae would be difficult to distinguish, it is shown that 

 the larvae of Plateumaris, here described for the first time, 

 are dissimilar from those of all other Donaciinae. The 

 larvae gnaw the roots of certain aquatic plants (Potamo- 

 geton, Sparganum, Carex, &-c.), and while doing so arrange 

 the head and prothorax so that the latter forms with the 

 plant a water-tight compartment in which the head can 

 work undisturbed by, and the food be kept from admix- 

 ture with, water and dirt. The mandibles of the larva 

 have a cutting, and not a crushing, edge ; they cannot be 

 used for grinding, and. in fact, serve only to make an 

 entry into the plant tissue, the sap of which then exudes 

 and is received by the laciniae of the maxillae and passed 

 backwards into the gut. The larvae seem to feed 

 exclusively on the sap ; an examination of the gut con- 

 tents, which consist of a homogeneous yellow fluid, shows 

 that cell-fragments are not present. The external features 

 of the head, the mouth parts, the muscles, and the 

 mechanism of feeding are considered in great detail. 



Aquatic insects have adopted various devices for obtain- 

 ing a sufficient supply of air: the larvae of the Donaciinae 

 have chosen a very remarkable one, namely, to tap the 

 reservoirs of air in the intercellular spaces of the sub- 

 merged parts of plants. .At the posterior end of the 

 nbdomcn is the " abdominal organ," which the author 

 shows to be a bifore spiracle. The terminal hook of this 

 organ is plunged into the vegetable tissue, air passes from 

 the latter into the organ, and apparently through thin 

 membranes into an atrium, which leads into the main 

 trachea. The spiracular slit in the abdominal organ serves 

 for expiration. 



The making of the cocoon is described at length. The 

 outer envelope is formed by a secretion of the whole body, 

 and is lined with a substance produced in four large 

 <Tcsophageal glands ; the larva gnaws one or two holes 

 through the bottom of the finished cocoon so as to make 

 connection with the air spaces of the root to which it is 

 attached ; air is thus secured for the pupal stage. The 

 author gives a list of the food plants of the different 

 species of larvae of this family found in Denmark, and 

 accounts of the gnawings, the sizes of the larvae at 

 different periods, the length of larval life, hibernation, the 

 flying period of the adults, the eggs, and the post- 

 embryonic development. The memoir forms a substantial 

 addition to our knowledge of the anatomy, biology, and 

 development of these interesting larvae. 



J. H. A. 



PHYSICAL ANTHROPOLOGY^ OF 

 A VSTRA LA SL\ N RA CES. 

 TN the Proceedings of the Royal .Society of Edinburgh for 

 the present session (k)io-ii) appears a scri's of four 

 ]>apors devoted to (he jihysical anthropoloffv of the races of 

 Australasia. The papers are by three authors, two of them 

 luiman anatomists, F'rof. R. J. Berry and Dr. .\. VV. VV. 

 Koljcrtson, the third a mathematician, Mr. K. Stuart Cross. 

 Ih" authors seek to fix the position of the Tasmanian and 

 .Australian natives amongst present and ^ast races of man- 



NO. 2169, VOL. 86] 



kind by applying biometrical methods to certain measure- 

 ments of the skull. 



The most valuable paper of the series is that by Dr. 

 Robertson, where he gives the data obtained from measure- 

 ments of 100 Australian crania. By applying Prof. Karl 

 Pearson's test for purity of race. Dr. Robertson finds the 

 native Australians are " pure " when the measurements of 

 the width of the cranium is considered, but " impure " 

 when the lengths are investigated. It will be seen that 

 Dr. Robertson's results are somewhat equivocal, and may 

 be quoted in support of either the unity or duality of the 

 Australian race. Similar methods applied to the Tas- 

 manian race show a much higher degree of homogeneity or 

 purity. The difference in purity between the Australian and 

 Tasmanian races may be explained by the fact that one is 

 spread over a large continent, while the other is confined 

 to a small island. 



An atteinpt is also made by the authors to fix the position 

 of the much-discussed Tasmanian race in the scale of 

 human evolution. The result will somewhat surprise those 

 who have sought to establish racial relationships on an 

 analysis and comparison of mere anatomical characters, 

 for by the methods here employed the Dschagga negro 

 comes out as the advance guard of the human race, well 

 in front of the European, while the native Tasmanian gains 

 a good place, being sandwiched between two ancient 

 Europeans — the man of Briinn and the Cro-magnon race. 



From an anatomical point of view the results are sur- 

 prising, for it would be hard to find g-reater cranial con- 

 trasts than those between the Tasmanian and Cro-magnon 

 on one hand, and the Tasmanian and Briinn on the other. 

 There can be no doubt, however, as to the high value of 

 the new data with which these papers supply anthro- 

 pologists. 



THE PRODUCTION AND IDENTIFICATION 



OF ARTIFICIAL GEMS.' 

 T PROPOSE to limit the term " artificial " to such 

 -'■ productions as possess the same chemical composition 

 and physical constants as the natural stones, differing from 

 them only in minute details consequent upon their being 

 produced in the laboratory instead of being dug out of the 

 earth, all other makeshifts being properly described as 

 " imitations." 



The scientific examination and identification of gems is 

 a matter of the greatest interest, but it would take far too 

 much time to discuss it in detail; and it is quite un- 

 necessary to do so, because it has already been brought 

 before the society most exhaustively by our chairman. Dr. 

 Miers.^ I propose, therefore, merely to remind you of the 

 main points. 



In order to bring this matter up to date, however, I 

 must refer briefly to one or two particulars in which 

 advance has been made since the time of these lectures. 



The most important properties of a precious stone are 

 those depending upon its refractive powers. Until recently, 

 the accurate determination of the refractive index of a 

 stone was a matter involving the use of complicated and 

 expensive instruments, and a matter for the skilled 

 mineralogist rather than the practical jeweller. It is true 

 that at the time Dr. Miers published his lectures there 

 existed an instrument known as the reflectometer, but the 

 determination of the refractive index with this was a 

 matter of some difficulty even in skilled hands, and its 

 value for commercial purposes was very small. Since that 

 time, however, thanks to the ingenuity of Dr. Herbert 

 Smith, this instrument has been improved out of all 

 recognition, and in its place we have the Herbert Smith 

 refractometer (Fig. i), by means of which anyone of 

 noriTial common sense can determine the refractive index 

 of a stone in a few seconds without even removing it 

 from its setting, and which, with a little practice, will 

 also enable one to determine with similar ease the amount 

 and kind of double refraction and the degree of dispersion. 



Taking the properties of precious stones as a whole, 

 the great point about them is the remarkable combination 

 of qualities ; it is not so much that they have optical 



' Abstract of a paper read before the Royal Society of Arts on April 26, 

 191 1, by Noel Heaton. 

 2 Cantor Lectures on Precious Stones, April, i?96. 



