July i8, 1895] 



NATURE 



28: 



I 



Branchiostomidas, by J. W. Kirkaldy (Plates 34 and 35), 

 enumerates two genera, Branchiostonia (as sub-genera, Am- 

 pliioxus, Heteropleiiron) and Asymmetron. A new species 

 of Heteropleuron, H. cingaleiise, is described. — On Sedgwick's 

 theory of the embryonic phase of ontogeny as an aid to 

 phylogenitic theory, by E. W. MacBride. 



June. — On the anatomy of Aliyoniuiii digitatuiii, by Prof. 

 Syihiey J. Ilickson (Plates 36-39), gives a brief account of 

 our knowledge of the anatomy of Alcyonium, the general morph- 

 ology, the English species, their geographical and hathymctrical 

 distribution, then the general anatomy, followed by the minute 

 anatomy of the ectoderm, nematocysls, stomodanun, mesenterial 

 filaments, mesogl<ea, spicules, endoderm, ovaries and testes, 

 the buds, concluding with a note on the circulation of the fluids 

 in the colony and on the digestion. In the history of investiga- 

 tions, Pallas' name is not alluded to, and yet he deserves to be 

 quoted as having even before .Savgny assigned correct characters 

 to Alcyonium (" Hi.s'. nat. des Coralliaires," Milne-Edwards, 

 tome I, p. 114), and the "Contribution a I'anatomie des 

 Alcyonaires," by Pouchet and Myevre, dates, if we mistake not, 

 before Vogt and Jung's account in their "' Lehrbuch," and while it 

 may be oflittle use to the student, it is not without interest, as it 

 figures, after a fashion, the nematocysts in A. digitalujii, and 

 this pos.sibly for the first time (1870). Prof. Ilickson, however, 

 leaves all previous writers far behind in his modern treatment of 

 this subject, and if he keeps his promise of publishing an account 

 of the maturation and fertilisation of the ovum and it" develop- 

 ment, he will leave us under still further obligations, for except 

 Kowalevsky and Marion's important papers on the develop- 

 mental history of Clavularia irassa and Sympodiutit coralloides, 

 we have but little light on Alcyonarian development. — Note on 

 the chemical constitution of the mesogloea of Alcyonium digita- 

 turn, by W. Langdon Brown. It is chiefly composed of a 

 " hyalogen " prior to the conversion of the hyalogen into 

 hyalin the mesogloea will yield a mucin; it also contains a 

 small amount of an insoluble albuminoid body, whose nature was 

 not determined ; it does not contain gelatine or nucleo-albtmien. 

 A sludy of metamerism, by T. H. Morgan. (Plates 40-43). 

 The author in a long memoir, that does not admit of being 

 briefly abstracted, thinks that the cases he cites show very 

 positively that the variations appearing in a radiate animal must 

 have come simultaneously and all together into the antimeres ; he 

 thinks few will doubt that the relation existing between repeated 

 organs in a radiate animal is at bottom the same relation 

 existing between the right and left sides of the body of a bilateral 

 animal. Mivart and Brooks have emphasised the further fact 

 that the relation between the right and left sides of the body is 

 the same relation that exists between the serially repeated parts 

 of a mctameric animal ; and he concludes that if this line of 

 argument be admitted, it puts the problem of metamerism into a 

 large category of well-established facts. — On the Ccelom, 

 genital ducts, ami Nephridia, by Edwin S. Goodrich. (Plates 

 44-45). The chief object of this paper is to call attention to the 

 theory, ** that the cavity which is known as the ccelom in the 

 higher Ccelomata is represented by that of the genital follicles 

 in the lower types of that grade." 



Aineriam Journal of Science, July. — On the pitch lake of 

 Trinidad, by S. F. Peckham. This pitch lake is situated near 

 the village of La Brea, on the Gulf of Paria. At first sight it 

 appearstobeanexpan.se of .still water, frequently interrupted 

 by clumps of trees and shrubs, but on a nearer approach it is 

 fouiul to consist of mineral pitch with frequent crevices filled 

 with water. The consistence of the surface is such as to bear 

 any weight, and it is not slippery nor adhesive. It is about 100 

 acres in extent. It occupies a bowl-like depression in a trun- 

 cated cone on the side of a hill covered with tropical jungles. 

 The cone consists of both asphalt and earth. A heavy stream 

 of asphalt has overflowed to the sea, forming a barrier reef for a 

 considerable distance. Asphalt has also overflowed to the 

 south, anil the general appearance of the escarpment .seems to 

 indicate that at some remote period the basin now occupied by 

 the lake had been filled some three feet higher than the present 

 level. It occupies what appears to be the crater of an old 

 volcano. Some diggings have been pu.shed to forty feet without 

 reaching the bottom. There is a steady outflow towards the 

 sea through the side of the cone. The Trinidad Bituminous 

 .■\sphalt Company have lately run a tramway from the pier 

 through the lake and back, so as to facilitate the removal of the 

 material. This tramway in crossing the lake is supported on 

 palm-leaves, some of which are 25 feet long, and this plan has 



NO. 1342, VOL. 52] 



answered every purpose. — On some reptilian remains from the 

 Triassic of Northern California, by John C. Merriam. The 

 author gives a descri]>tion (jf some of the few Californian Mesozoic 

 reptiles. One of these resembles Ichlliyosaurus, while the other 

 is described as Sliastasaunis Pacijicus. — .\ further contribution 

 to our knowletlge of the Laurentian, by Frank D. Adams. This 

 paper is accompanied by a map of a ])ortion of the edge of the 

 -\rchean prolaxis north of the island of Montreal, Quebec. 

 There are in the dislrict considered at least two distinct sets of 

 foliated rocks. One of these represents highly altered and 

 extremely ancient sediments, while the other is of igneous 

 origin. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, .May 16. — " On Measurements of .Small 

 Strains in the Testing of Materials and Structures." By Prof. 

 J. A. Ewing, F. R.S. 



The paper describes a new form of "extensometer," or 

 apparatus for measuring the elastic stretching of bars subjected 

 to pull in the testing machine or otherwise. .At the two ex- 

 tremities of the length under test, which is usually eight or ten 

 inches, two cross-pieces are attached to the rod by means of a 

 pair of diametrically opposed set-screws. Each piece is 

 separately free to oscillate about the line joining its screw points, 

 since it touches the rod under test at no other place, but the 

 two pieces are caused to engage with each other in such a way 

 that when the rod extends the end of one of the pieces becomes 

 displaced through a distance which is proportional to the exten- 

 sion. The amount of this displacement is measured by means 

 of a microscope attached to the other piece. The whole ap- 

 paratus is self-contained, and the parts are arranged to have no 

 unnecessary constraint. Its indications show the mean extension 

 taken over the whole section of the rod, and are independent of 

 any small amount of bending or twisting which the rod may 

 undergo as it is stretched. The microscope is ftirnished with an 

 eye-piece micrometer which reads the extension to j-jjJijTT inch, 

 and a calibrating screw is provided for testing and setting the 

 micrometer scale. Two forms of the instrument are described, 

 one suitable for laboratory use when the specimen under test 

 stands vertically, and the other applicable to rods in any position, 

 such as the members of bridge or roof frames in situ. In the 

 laboratory use of the in.strtnnent the elastic properties of the 

 material are examined by observing the strains under known 

 loads ; in the application to structures the object is to determine 

 experimentally what the stress on any member is, from observa- 

 tion of the strain, the modulus of elasticity being assumed. 



The author describes a number of observations made with the 

 new extensometer, chiefly on rods of iron and steel. The 

 following readings refer to successive loadings of a bar of steel, 

 which conforms closely to Hooke's Law, the loads being well with- 

 in th° primitive elastic limit. They serve to illustrate the sensibility 

 of the instrument. The zero of the extensometer was set at 400, 

 and the unit of its scale was stjJt;, inch. The bar was i\ inch 

 in diameter, and the length under test was 8 inches. 



In other experiments the rod under examination was allowed 

 to become overstrained, that is to say the load was increa-sed 

 until the elastic limit was passed and permanent set was produced. 

 In this condition the elastic properties of the rod are materially 



