32 



KNOWLEDGE. 



January, 1911. 



Mr. M. J. Allan, of Geelong, sent a slide of spicules of a species 

 of Gorgonia unknown to him concernins the identification of 

 which he sought information. He also sent some slides 

 mounted in fluid iiy a method of his own. He likewise 

 mentioned in a letter that four years ago he had devised a 

 variable eye-piece giving three magnifying powers, which he 

 offered to send for inspection. Mr. Merlin sent, for exhibition, 

 three photomicrographs of Gravson's Rulings, which Mr. 

 Grayson had sent'him. They showed the 100,000. 110,000, 

 and 120.000 bands of Grayson's twelve-band plate. Previously 

 no photograph had ever been exhibited of anything o\er 

 112.595 lines to the inch. Dr. Butcher exhibited a number 

 of photomicrographs of diatoms, Coschiodisciis astcroin- 

 plialus and C. omphalanthus, Navicula Smithii. Pinnii- 

 laria cardinalis and Triceratiuin favus. The photographs 

 were taken in series and represented successive focal planes 

 of each object. The conditions under which they were taken 

 were given. 



Mr. A. F,. Hilton exhibited a number of nmunted specimens 

 of British Mycetozoa. In reference to liis exhibit he said that 

 at the present time the disposition was to classify the 

 Mycetozoa among the Rhizopoda, but their metamorphoses 

 marked them off as an entirely distinct group. Their life- 

 history presented three principal phases — aquatic, amoeboid, 

 and aerial. The question of the sexuality of the Mycetozoa 

 was a very obscure one. In all three phases there were 

 nuclear divisions. 



The President made a communication on Japanese 

 Pennatulids, and exhibited some typical specimens of great 

 beauty. He said that he had been entrusted ijy Professor 

 Ijima, of Tokyo University, with a collection of Pennatulids, 

 on the study of wliich he was at present engaged. His report 

 was not yet ready for publication, but he had thought that it 

 would be of interest to the Fellows of the Society to see a 

 representative sample of these beautiful Sea- Pens. They 

 would understand, when they looked at the dimensions of the 

 specimens, why it was necessary on a long railway journey to 

 be content with a sample of the collection. 



The Pennatulacea, or Stelechotokea. include some of 

 the most beautiful of fixed marine animals — long graceful 

 colonies, often plume-like, as their name suggests, with rich 

 colouring, and with strong luminescence. They live fixed on 

 the floor of the sea, and many of them show a famihar 

 adaptation to life on the bottom — long stalks raising the 

 polyp-bearing portion off the substratum. In deep-water 

 forms, such as the beautiful Umbellulas, the proportion of 

 sterile stalk to polyp-bearing rachis reaches an extreme. 



The Pennatulids were related to Alcyonarians, such as Dead 

 Men's Fingers, Precious Coral, Organ-Pipe Coral, the Gor- 

 gonids and the Gorgonellids, like HicksoncUa, which Mr. 

 Simpson had established as a new genus at the last meeting of 

 the Society. They differed markedly, however, in several 

 respects. In a very remarkable way the primary polyp, 

 which developed from the fertilized egg, was sacrificed to 

 forming the main axis on which the secondary polyps were 

 borne, which in turn might give off (always through the 

 intermediation of stolons or solenia) tertiary polyps and so on. 

 A central rod. which was present in the majority as the skeletal 

 support of the colony, ran up the middle of the gastric cavity 

 of the primary polyp, and some authorities regarded it, there- 

 fore, as endodermic in origin, whereas the skeletal support of 

 all related forms is ectodermic. Thirdly, the Pennatulids 

 almost always showed a pronounced dimorphism — along with 

 the ordinary polyps or autozooids there were dwarf polyps 

 without tentacles, the siphonozobids, whose office it was to 

 keep currents of water going in the canals of the colony. 

 It should also be noted that there was in Pennatulacea a 

 marked tendency to bilateral arrangement of the polyps, similar 

 to the arrangement of barbs on a feather. 



The President also read two papers by Dr. J as. F. Gemmill, 

 (1) "Aerator for small Aquaria," (2) "Adaptation of Ordinary 

 Paraffin Baths for Vacuum Embedding." Mr. J. E. Barnard 

 read papers " On the Use of a Metallic Electric Arc in 

 Photomicrography," and on "A Simple Method of obtaining 

 Instantaneous Photomicrographs." 



THE EFFECT OF GRAVITY ON EUGLENA VIRIDIS 

 EHRB. — At the Meeting of the Royal Society held on 

 November 17th, Harold Wager, F.R.S., gave the results of 

 some experiments on the movements of micro-organisms. 

 Eiiglciia viridis, when placed in the dark in shallow vessels 

 or narrow tubes, becomes aggregated into network-like patterns 

 or more or less well-defined circular groups. If a narrow tube 

 filled with water containing sufficient Euglenae to give it a 

 pronounced green colour be placed horizontally in the dark or 

 in a weak light, the aggregation takes the form of a series of 

 nearly equally spaced groups like green bands crossing the 

 tube from one side to the other. Each group shows clearly 

 two distinct regions, a central denser one consisting of 

 cells moving downwards, and a lighter peripheral area 

 consisting of cells moving upwards. There is, in fact, a 

 constant cyclic movement, which is kept up so long as the 

 aggregation persists. Examination with a pocket lens shows 

 that, as the organisms reach the bottom of the stream, they 

 gradually separate from one another, and begin to move 

 upwards. As they reach the upper surface, they are seen to 

 be drawn towards the central denser region of the group, 

 and again enter the downward stream. This aggregation, with 

 its regular cyclic movements, may persist for several days, 

 provided the t'uglenae are kept in the dark or under red glass. 



The downward movement appears to be a purely mechanical 

 one, dependent upon the specific gravity of the organism, and 

 is not due to a stimulus which evokes a physiological response 

 as in geotropism or geotaxis. The upward movement is, on 

 the other hand, due partly to the activity of the organisms 

 themselves, partly, no doubt, to the currents set up in the liquid 

 by the friction of the downward moving stream. The upward 

 movement of Englcna appears to be controlled, so far as the 

 orientation of its elongate body is concerned, by the action 

 of gravity. 



The network-like aggregations and groupings resemble ver\- 

 closelv the cohesion figures which are formed, under certain 

 conditions, when fine sediment is allowed to settle slowly in a 

 ■ 'uid, and the conclusion has been arrived at that the 

 r.,gregations are probably of the nature of cohesion figures, 

 due to the action of gravity upon organisms massed together, 

 combined with the vortices set up by the streaming movements. 



The movements of certain micro-organisms are therefore 

 controlled in a purely mechanical fashion, and the advantage 

 to those species which, like Eiiglcna, are often found in a 

 confined space in large numbers, must be very great, as by its 

 means a constant circulation is maintained, and they are 

 prevented from accumulating in such dense masses as would 

 be detrimental to their existence by interfering with their 

 assimilatory or respiratory functions. 



PHOTOGRAPHY. 



By C. E. Kenneth Mees, D.Sc. 



INFRA-RED PHOTOGRAPHS.— .A recent holiday trip 

 to Portugal gave me an opportunity of trying some landscape 

 photographs taken by infra-red light after the manner 

 suggested by Professor R. \V. Wood. 



A filter was prepared which passed only light abo\e 

 7,250 A.U., and through which, therefore, only a ver.\' faint 

 amount of deep red light could be seen by screening the eye 

 thoroughly. 



The plates which were used had a sensitiveness extending 

 with long exposures to 7,600, so that the region used with the 

 plates and screen was situated between the a and A lines, from 

 7,250 to 7,600. 



The nniltiplying factor of the screen on these plates was 

 found to be about three thousand, so that, as a normal 

 exposure at F. 8 in sunlight would have been about one-tenth 

 of a second, the infra-red photographs required an exposure 

 of five minutes. 



Unfortunately the peculiarities of the Portuguese small boy, 

 and the very limited time at my disposal, tended to cut 



