458 



NATURE 



[April 6, 1876 



The Prince of Wales is bringing home with him a large col- 

 lection of living animals, including, among the most important, 

 two Musk Deer, three Thars, a Manis, three adult Ostriches, 

 four Elephants, five Tigers, three Leopards, sixteen Impeyan 

 Pheasants, more than twenty Tragopans and Cheer Pheasants, 

 several other Deer and Antelopes, together with Fruit Pigeons, 

 Peafowl, &c. These His Royal Highness intends to have exhi- 

 bited as one collection, and as such they will be deposited in the 

 Gardens of the Zoological Society, a suitable house being in 

 course of erection, and now nearly completed, for their 

 reception. 



The additions to the Zoological Society's Gardens during the 

 past week include a Lesser White-nosed Monkey ( Cercopitheais 

 petaurista) from West Africa, presented by Mr. F. Ward ; a 

 Common Marmoset {Hapale jacchus) from South-east Brazil, 

 presented by Mrs. Cleaver; a Wild Sheep {Ovis burrhel), an 

 Impeyan Pheasant {Lophophorus impeyanus) from the Hima- 

 layas, deposited ; two Wheatears {Saxicola cenanthe), European, 

 purchased; two Cuming's Octodons {Octodon cumingi) born in 

 the Gardens. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, March 23. — "Description of a Mammalian 

 Ovum in an early condition of Development," by E. A. Schifer, 

 Assist. Prof, of Physiology in Univ. College. 



The author describes the ovum of the cat from five, in the 

 stage where they were rendered evident as scarcely perceptible 

 swellings in the comua uteri. In their long axes they were \ inch 

 long ; in their short, xr iiich. No mesoblast was anywhere 

 present between the hypo- and epiblastic layers, which latter were 

 clearly separable from one another and nearly in contact only in 

 a small part, where only the cells of each were in more than 

 single layers. At this spot also, the cellular elements of each 

 layer being perfectly recognisable, an exquisitely fine pellicle, 

 which in section appears as a mere line, passes over and forms 

 a definite boundary to the outer surface of the hypoblast at the 

 thickened area. This is named the metnbrana limitans hypo- 

 blastica, and is found to be perfectly homogeneous and con- 

 tinuous, becoming stained slightly with carmine, and is probably 

 a cuticular formation produced by the underlying cells. This 

 structure seems to have been as yet unnoticed ; the mesoblast 

 cells without doubt first appear outside it, which is in favour of 

 the epiblastic origin of that layer. 



" On the nature of the force producing the motion of a body 

 exposed to rays of heat and light," by Arthur Schuster, Ph.D., 

 Demonstrator in the Physical Laboratory of Owens College. 

 Communicated by B. Stewart, F.R.S., Professor of Natural 

 Philosophy in Owens College, Manchester. 



Mr. Crookes has lately drawn attention to the mechanical 

 action of a source of light on delicately suspended bodies in 

 vacuo ; I have made a few experiments with the view of finding 

 out the seat of the reaction which evidently must tend to move 

 either the enclosure or the source of light. I have found that 

 the action and reaction is entirely between the light bo.'.i s sus- 

 pended in vacuo and the exhausted vessel. 



Mr. Crookes' "Light-Mill" was suspended by means of two 

 cocoon fibres, forming a bifilar suspension from the top of a 

 vessel which could be exhausted. A slight movement of the 

 enclosure could be easily detected by means of a concave mirror 

 attached to it. A beam of the oxyhydrogen lamp was concen- 

 trated on the light-mill, which then revolved about 200 times a 

 minute. 



The Ught was cut off at the beginning of the experiment by 

 means of a screen, and the position of rest of the glass vessel was 

 read off by means of the dot of light on the scale. The screen 

 was then suddenly removed, and in every case a large deflection 

 of the glass vessel was observed. The vessel was deflected in 

 the opposite direction to that in which the mill turned. When 

 the velocity of the mill had become constant, the vessel returned 

 to its original position of rest, but on suddenly cutting off the 

 light the vessel was again deflected, but in the opposite direction 

 as on starting the experiment. The vessel therefore now turned 

 in the same direction in which the mill turned. 



These experiments are easily explained on the assumption that 

 the force acting on the vessel enclosing the light-mill is exactly 

 equal and opposite to that a,cting on the mill itself. While the 

 velocity of the mill in one direction is increasing, a force acts in 

 the opposite direction on the vessel. When the velocity has 

 become constant, the force which tends to drive the mill round 

 is exactly counterbalanced by the resistance which opposes the 

 motion of the mill. The two forces acting on the vessel will 

 therefore counterbalance, and the vessel will return to its original 

 position of rest. When the light is cut off, the resistance will 

 stop the motion of the mill. The reaction of the resistance will 

 act on the enclosure, and the enclosure will turn in the same 

 direction as the mill. 



By means of the reaction on the enclosure I have been able to 

 calculate the strength of the force ; and I have found that the 

 pressure on a surface on which the hght of equal intensity to that 

 used in my experiments falls is equal to that produced by the 

 weight of a film of water equal in thickness to the length of a 

 wave of violet light. 



March 30. — " On the Placentation of the Lemurs," by Wm. 

 Turner, M.B. (Lond.), Professor of Anatomy, University of Edin- 

 burgh. Communicated by Prof. Huxley, Sec. R.S. 



In the introduction to this memoir a description was given of 

 the observations made by M. Alphonse Milne-Edwards on the 

 gravid uteri of several genera of lemurs. The author then pro- 

 ceeded to describe the gravid uteri of six lemurs which he had 

 received from Dr. Andrew Davidson, of Antananarivo, Mada- 

 gascar, viz., Propithetus diadema, Lemur rufipes, and Indris 

 brevicaudatus. He then summarised the conclusions he had 

 arrived at in the course of his dissections, and showed that the 

 placenta in these animals was diJused, and presumably therefore 

 non-deciduate. The paper concluded with a discussion of the 

 bearing of these observations on the classification of the lemurs, 

 and on the theory of the descent of the deciduate mammals from 

 a primaeval root-form of Prosinise. 



" The Residual Charge of the Leyden Jar," by J. Hopkinson, 

 M.A., D.Sc. Communicated by Prof. Sir William Thomson, 

 F.R.S. 



Linnean Society, March 16. — Prof. Allman, president, in 

 the chair. — Messrs. Edward R. Alston and David Blair were 

 elected Fellows of the Society. — Dr. J. Anderson communicated a 

 note "On the plastron of the Gangetic Mud-turtle, Emyda dura," 

 detailing an instance where eleven instead of the usual nine bones 

 were present. This occurred in an embryo from the egg, and it 

 further appears that ossification and coalescence of the extra 

 pair of bones is coincident with birth. — Mr. A. W. Bennett 

 read a paper " On the rate of growth of the flower-stalk of the 

 hyacinth, " in which he showtd that the greatest energy of growth 

 is in the lowermost part of the stalk. This agrees with the 

 recorded observations respecting the relative growth of different 

 nodes of a stem, where the greatest energy is always at a con- 

 siderable distance from the apex. But it offers a contrast to the 

 phenomena exhibited in the submerged flower-stalk of Vallis- 

 neria, where the greatest encgy of growth is in the terminal 

 portion beneath the flower-bud. — Mr. Francis Darwin laid before 

 the Society the results of his observations "On the hygroscopic 

 mechanism by which certain seeds are enabled to bury them- 

 selves in the ground." These related chiefly to the Feather-grass, 

 Stipa pennata, but similar phenomena obtain in other grasses, in 

 Anemone montana and certain of the Geraniaceoe (as Hanstein 

 has recorded, 1868). The essential structures are — a sharp point 

 with reflexed hairs, and a strong woody awn, so bent as to pos- 

 sess a lower vertically helical and an upper horizontal part. 

 With moisture the spiral .portion of the awn untwists, causing 

 the horizontal part to revolve, while the flexure between them 

 disappears and thus straightens the awn. A reversal of this pro- 

 cess succeeds on the awn becoming dry. In the case of 

 Stipa the long, feathery, horizontal part of the awn is easily 

 entangled in low vegetation, and the seed retained verti- 

 cally, with point on the ground. With wetting the awn 

 untwists, but the horizontal part prevented from revolving, 

 the rotation is transferred to the seed, which latter has 

 superadded pressiire of its point, by a conversion of the awn 

 to straighten itself. Again, as the awn dries the seed is not 

 pulled out of the ground, but curiously enough is thrust deeper 

 down ; the reflexed hairs being subservient. By such combina- 

 tions and alternate actions complete burial of the seed ensues. 

 The special advantage of seeds being thus imbedded is obscure ; 

 in Stipa being unconnected with germination, though possibly a 



