September. 1910. 



KNOWLEDGE. 



369 



arisen. The life-history of the uniceUular form Chlamydo- 

 monas is described in detail, and its resemblance in many 

 respects to the Polyblepharidaceae. which latter show a very 

 marked mixture of Chlani\-domonad and Flagellate character- 

 istics. The connecting link with the Flagellates is, according 

 to the author, by way of the Cryptomonadineae which, in 

 the possession of chlorophyll and in forming starch show 

 significant analogies to the green algae. From the unicellular 

 the ne.\t step is to such forms, as Goiiiiiiii which may be 

 described as a colonial Clilaniydoiiioitas. and the marvel 

 of perfection in this respect, the genus Volvox. This series 

 affords a very striking example of recapitulation in the 

 invariable recurrence of the flat go;N';(/j!-forni in the early 

 phases of development. In the second section the author deals 

 with the higher filamentous types, such as the Siphonales and 

 the Ulotrichales. both of which are probabl\- de\eloped from 

 a Protococcaceous stock. 



A NEW TRYPANOSOME.— In Xatiirc. for August 4th, 

 Professor E. A. Minchin describes a new Trypanosome 

 parasitic in human blood. Its discoverer. C. Chagas, first 

 observed it in the digestive tract of a bug infesting the huts of 

 the poorer people in Brazil, and afterwards found numerous 

 trypanosomes in the blood of the human beings dwelling in 

 this area. The life-cycle of Scliizotrypnniim cnizi shows 

 some peculiarities not yet known in any other species. These 

 differences being that there is an intracorpuscular phase in its 

 development, and that the new species exhibits schizogony or 

 multiple fission ; this latter phase takes place in the lungs of 

 experimentally inoculated animals, and it is during this stage 

 the disease proves fatal. 



THE QUEKETT MICROSCOPICAL CLUB.— At the 

 gossip meeting, on August 9th. Mr. Hilton w-as showing speci- 

 mens of the Mycetozoa. An example of Lantprodcniia 

 arcyrionenia was particularly beautiful: under incident light 

 and a low power not only was the elegant form well displayed, 

 but the outer coat of the sporangium shone with a metallic 

 lustre resembling gold, finely contrasting with the dead black 

 capillitium within, which appeared where portions of the 

 covering had become detached. Mr. Draper exhibited, under 

 a binocular, the singular and not \ery common rotifer Pcdalion 

 miruin. Its extraordinary appearance makes it a striking 

 object, especially when \iewed under a binocular. Another 

 member exhibited several slides showing the non-sexual 

 reproduction of mosses by means of small bulbs formed 

 on the stems and rhizoids, and "' gemmae " either in cups 

 on the ends of the stems as in Tetraphis. or seated directly 

 on the stem as in Aulacoiiiiiioii. The brilliant red colour 

 of the bulbs in comparison with the green stems made a 

 beautiful object, especially when shown with the dark blue back- 

 ground obtained by a Rheinberg colour disc placed under the 

 sub-stage condenser. This method of illumination is looked 

 at askance by some serious microscopists as being merely a 

 concession to the desire for prettiness ; but in its defence it 

 may be urged that, while giving a beautiful effect, when, as in 

 the present instance, the natural colours of the object are 

 brought out sharply by the darker background, at the same 

 time, details not otherwise easily seen, are at once made 

 noticeable ; also, that the deeper colour of the background is 

 less tri,-ing to the eyes than the glare, a certain amount of which 

 is inevitable with the ordinary method of illuminating trans- 

 parent objects. J.B. 



DESMIDS AT THE EXHIBITION.— On a recent visit 

 to the Japan and British Exhibition, Shepherd's Bush, it was 

 noticed that on the surface of the water of the canals and 

 lagoon there was a very considerable amount of some green 

 floating matter. Various species of OsciUatoria and other 

 My.xophyceae are common in such situations, but examina- 

 tion proved that in this case the substance was mainly 

 composed of a small Desmid. The cells were held together 

 in larger or smaller masses by a clear colourless jelly ; often 

 this was about J-in. thick, the under side having a small 

 amount of soil and dirt adhering to it. It had evidently been 

 formed on the slight quantity of mud and sediment at the 

 bottom of the water ; then, owing to sunUght and warmth, 

 the plants had gi\"en off gas which entangled in the jelly- 



like substance, had floated the whole to the surface. The 

 Desmids belong to the large genus Cosntariuni and were 

 probably C. ititidtiliiin, though the identification is made 

 with some hesitation, a detailed account of the genus — a 

 somewhat uncertain one — not being accessible at the moment. 

 Each plant consists of a flattened cell of approximately 

 circular outline, deeply notched, and almost divided by a sinus 

 in the middle into two nearly semi-circular halves. There is 

 a chloroplast. usually fan-shaped, that of the two hahes being 

 connected by a narrow band, the colour a bright pale green, 

 and a very e\ident round body Ipyrenoid) in each half. The 

 surface of the cell is smooth, length about 27M, breadth about 

 22m. After being kept in a small aquarium in a window 

 for a few days, many of the Desmids are beginning to 

 propagate. The chlorophyll in each semicell contracts a 

 little and leaves the narrow- connecting portion. The two seg- 

 ments of the plant separate slightly, and each puts out a small 



A B C 



projection of clear protoplasm. This gradually increases in size, 

 so further separating the two parts of the parent, and, at the 

 same time, assuming the shape of the mature semicell. When 

 the new' parts are about half grown some of the chlorophxU 

 passes into them from the parent, and they gradually attain 

 full size and de\"elopment. When this stage is reached there 

 are two complete but connected plants, each consisting of an 

 original and new semicell. and finalh'. the two entirely separate. 

 The figure above shows the mature plant A, the 

 commencement of division B, and a more ad\anced 

 stage of the process C. Besides the Desmids there were 

 several other small algae usually found in companionship 

 with them, Scenedesnius obliqitiis and S. qiiadricaitda, 

 and varieties being noticed. J. B. 



P H OT( )G R A P H Y-P U R P: an d A P P L I K 1 ). 



By Chapm.^n Jones, F.C.S., F.I.C. 



THE BRUSSELS CONGRESS.— The fifth International 

 Congress of Photography held its meetings during the first 

 week in August. Judging by the number of communications 

 received and the various nationalities represented, it was the 

 most successful congress of the series. The subjects dealt 

 w'ith were so various that it is impossible in a short note to 

 give any general idea of the proceedings, but I shall hope to ' 

 give, from time to time, references to some of the communica- 

 tions that are likely to prove of interest. The following 

 note refers to papers read at the Congress. 



INSTANTANEOUS AUTOCHROMES.— M. C. Simmen 

 has succeeded in increasing the sensitiveness of autochrome 

 plates by eight times, so that useful exposures may be made 

 with large aperture lenses in from the tenth to the fiftieth of a 

 second in a good light out of doors. This is effected by 

 bathing the plates in a solution that renders them much more 

 sensitive to red — a bath containing pinaverdol or pinacyanol. 

 Plates so treated are a great deal more sensiti\e to the red up 

 to a w^ave length of 7,000, and show maxima at 5,350. 5,750, 

 and 6,300. It is therefore necessary to use a different 

 compensating screen from that usually employed, but 

 the author finds that by following his instructions the 

 colour sensitiveness of the prepared plates is so well 

 balanced that it is only necessary to stop the ultra- 



