July. 1911. 



KNOWLEDGE. 



281 



From the facts detailed in the paper the author deduces the 

 following chief conclusions : — 



All bacteria which have been adequately investigated are — 

 like all other Protista — nucleate cells. The form of the 

 nucleus is variable, not only in different bacteria, but also at 

 different periods in the life-cycle of the same species. 



The nucleus may be in the form of a discrete system of 

 granules Ichromidia) : a filament of variable configuration; in 

 the form of one or more relatively large aggregated masses of 

 nuclear substance ; of a system of irregularly branched or bent 

 short strands, rods or networks: andprobablyalsoin the vesicular 

 form characteristic of the nuclei of many animals, plants and 

 protists. There is no evidence that enucleate bacteria exist. 

 Finally, in addition to these purely morphological conclusions 

 concerning the nucleus, the author thinks it is highly probable 

 that the bacteria are in no way a group of simple organisms, 

 but rather one displaying a high degree of morphological 

 differentiation, coupled, in many cases, with a life-cycle of 

 considerable complexity. 



THE GENUS POLYTREMA iFOR.\MlXIFER.-\i.— 

 At the meeting of the Linnean Society, held on May 

 4th, Professor Sydney J. Hickson. F.R.S., communicated 

 a revision of the above genus. The discovery of some very 

 large specimens of Foraminifera belonging to the species 

 described by Carter as Polytrciiur cylindricuiit in the material 

 collected by Professor Stanley Gardiner in the Indian Ocean, 

 led the author to make a careful examination of this and of 

 other species attributed to the genus Polytrenia. The result 

 of this examination was to prove that the specimens usually 

 labelled Polytrciuci in collections may belong to three ([uite 

 distinct genera. 



Polytrenia cylindriciiin of Carter is the type of a genus 

 for which the generic name Sporadotreiiia is proposed. 

 The specimen described by Carpenter under the name 

 Polytrenia rubra Lamk.. and many others that are labelled 

 Polytrema ininiaccuin Pallas, in collections, belong to 

 another genus for which the generic name Ho»;o/rc'/»(r is pro- 

 posed. The specimens described by Merkel. Lister and others 

 under the name Polytrenia niiniacciiin belong to a genus 

 distinct from the other tw^o. and for this it is proposed that the 

 generic name Polytrenia be retained. 



A description of the principal characters separating the three 

 genera is given in the paper. 



.\s regards the geographical distribution of the three genera, 

 it may be observed that Sporadotreina has only been found 

 in the Indian Ocean and on the Macclesfield f5ank in the 

 China Sea. that Polytrenia and Honiotrenia appear to have 

 a much wider distribution in temperate and tropical seas, but 

 atpresent the author has not seen any specimens of Polytrenia 

 from the shores of the American continent, nor has he seen 

 any specimens of the genus Honiotrenia from the Mediter- 

 ranean Sea. 



COCCIDIOSIS IN GROUSE.— In an interesting paper 

 contributed to the current number of Science Progress. 

 Vol. \'.. pages 565-583. on the diseases of Grouse, Professor 

 .\rthur E. Shipley, F.R.S.. describes the complex life history of 

 Eiineria \Coccidiuin) avium, one of the seven distinct 

 unicellular or protozoan parasites which live either in the 

 intestines or in the blood of the grouse. 



The chief source of contamination on the moors is the 

 droppings of other diseased grouse. The droppings contain 

 thousands of cysts (oocysts) or spores of the parasite and 

 these spores, with their hard coats, are extremely resistant 

 and can endure for very long periods w-ithout the death of 

 their contents, which gradually divide to form four smaller 

 spores (sporocysts) inside. The spores are scattered over the 

 moors by the action of the wind and rain and. alighting on 

 the heather or in the tarns of the moors, are taken up by the 

 grouse in their food or drink. When the cysts are swallowed. 

 they enter the gizzard of the bird and pass unchanged into 

 the first part of the intestine, called the duodenum. Here the 

 pancreatic juice is poured into the intestine, to aid in digestion. 

 and under its influence the cyst-wall is softened and dissohed. 

 and the four small spores (contained within the ripened spore 



or oocyst) are set at liberty. Each small spore contains two 

 active motile sporozoites. which emerge from the softened 

 spore-case and proceed to penetrate the epitheliimi of the 

 duodenum. The young parasites ultimately cause the 

 destruction of the lining of the first part of the small intestine 

 — the region where, normally, the most active digestive pro- 

 cesses occur. The Coccidiiini parasities multiply in the 

 duodenal epithelium and then invade the caeca or "blind-guts," 

 with disastrous results. 



Sooner or later a limit is reached, on the one hand, to the 

 power of the grouse chick to provide nourishment for the 

 parasites, and on the other to the multiplicative capacity 

 of the parasites themselves. The Coccidiiini then begins to 

 reproduce sexually. Many small male parasites are produced, 

 together with larger food-containing female Coccidia. The 

 male and female parasites conjugate and then encyst, bursting 

 through into the cavity of the gut and giving rise to the spores 

 found in the caecal droppings on the moors. 



PROTOZOA OF THE SOIL.— At the meeting of the 

 Royal Society held June 1st, 1911, a paper was read by T. 

 Goodey forming a contribution to our knowledge of the 

 protozoa of the soil. 



It gives an account of work carried out on the soil protozoa 

 which .are considered to be chiefly instrumental in limiting the 

 activity of bacteria in the soil and thus in helping to render 

 the soil comparatively infertile. Methods of obtaining 

 protozoa in cultures of soil are described, and a list of the 

 different species found so far is given. An experimental 

 method for quickly finding the earliest ciliated protozoa 

 occurring in a soil culture is described, in which use is made 

 of the galvanot.actic response which many of the protozoa show 

 when stimulated by means of a continuous electric current. 

 By means of this method, active ciliated protozoa have been 

 found in from lA hours to 4 hours. 



Experiments on the length of time required for a ciliated 

 protozoon Colpoda citcitlliis to develop from its resting cysts 

 ha\'e also been conducted in similar media and at the same 

 temperature as used in the soil cultures. It has been found 

 that the times required for development in both soil and cyst 

 cultures are comparable, and that the first Colpoda ciiciiltiis 

 to occur in soil cultures are almost identical in appearance 

 with those which emerge from resting cysts. 



The conclusion drawn from the experiments is that the 

 ciliated protozoa are only present in the soil in the encysted 

 condition, and do not. therefore, function as the factor limiting 

 bacterial activity in the soil. 



The protozoa of the soil are referred to in a paper by Dr. 

 H. B. Hutchinson (see "Knowledge" N.S. Vol. VIII, 

 pages 123-126. 



(JUEKETT MICROSCOPICAL CLUB.— May 23rd, 

 igfl. Dr. E. J. Spitta, F.R.A.S., F.R.M.S.. vice-president, in 

 the chair. Mr. C. D. Soar. F.L.S.. F.R.M.S., read a paper 

 on "The work of the late Saville-Kent on British Hydrach- 

 nids." Together with Mr. Williamson, of Edinburgh, the 

 author is preparing a monograph of British Hydrachnids. and 

 had obtained from the British Museum (Natural History) 

 Authorities permission to examine all the slides, notes and 

 drawings which Mr, Saville Kent had brought together. The 

 collection was begun in 1S67. Mr. Soar found it possible to 

 identify forty species from the mounted preparations, and a 

 further ten from various notes and drawings. A detailed 

 list of the species identified is added to the paper. 



A paper by Mr. E. M. Nelson. F.R.M.S., on " Methods of 

 Illumination" was read by the honorary secretary. Mirror 

 illumination was first dealt with. The proper way to centre a 

 concave mirror is : — First focus the object, then, looking at 

 the eye-lens, by moving the mirror, bring the image of the light 

 source central in the Ramsden disc. It is better to have centred 

 illumination even at the expense of an incompletely lighted 

 field. The use of ground glass then received attention, and 

 surprise was expressed at the appreciative remarks made by 

 Dr. Carpenter and Lewis Wright in their well-known books, 

 when discussing the use of this medium. After exhaustive 

 trials of ground-glass, and particularly in relation to its effect 



