152 



KNOWLEDGE. 



Apru,, 1911. 



passed from parent to offspring. The parent leeches were 

 invariably infected with tr\-panosonies derived from the fish in 

 the reser\oir, wtrich frequentl\' showed these parasites in their 

 blood. 



The trypanosomes of perch, bream and goldfish were fonnd 

 to complete their cycle in Hciiiiclcpsis. and conld be 

 transmitted to clean goldfish by means of leeches. The 

 specimens used in these experiments were always j'oung 

 laboratory-hatched Hciiiiclcpsis. The trypanosomes of pike 

 and rudd also complete their cycle in this leech, but the 

 opportunity of passing these two forms into goldfish did not 

 present itself. The cycles of the trypanosomes derived from 

 these different sources are apparently identical. Thr main 

 features are as follows : — 



The trypanosomes taken into the crop of the leech along 

 with the blood multiply very rapidly, undergoing a marked 

 change of form. After some days slender forms begin to 

 arise. These increase in number, and at the end of digestion, 

 some time after the blood has quite disappeared, they come 

 forward and lie in the proboscis-sheath in very large numbers. 

 The form found in the sheath is a very slender, long creature 

 of quite definite type : division has never been obser\ ed in 

 this phase. 



When the leech feeds once more, these individuals are 

 inoculated into the fish. The proboscis-sheath is always 

 cleared of trypanosomes by one feed. After a clean feed the 

 slender inoculative type of trypanosome disappears from the 

 crop of an infected leech, and the infection is carried on b\- 

 short, broad forms. Conjugation has never been observed. 



If water is added to the blood of fish containing trypano- 

 somes. the flagellates divide after a number of hours, probably 

 in response to lowering of osmotic pressure in the fluid in 

 which they find themselves. 



KOVAL MICROSCOPICAL SOCIETY.— Februarv 13th. 

 lyll, Mr. H. G. PHmmer. F.R.S., President, in the chair. 

 — Messrs. E. Heron - Allen and Arthur Earland read a 

 paper illustrated by a series of lantern slides on new or rare 

 species of Foraminifera found in the shore-sands of Selsey 

 Bill, Sussex. The authors called attention to the identity of 

 the fossil Foraminifera of the Bracklesham Beds with the 

 living species found in Australian shore-sands. Recent 

 specimens of Bolivina diirrandii Millett and PnJvinuliita 

 vcnniciilata Brady, were shewn, the only other known records 

 being as regards the former from the Malay Archipelago, and 

 as regards the latter from tropical and sub-tropical seas. In 

 addition to these, Milioliiia suborhiciihiris. M. rotunda, 

 Tcxtuhtria inconspicna. var jugosa, Bolivina turtnosa, 

 Uvigcriiia aspcnila, and Sagraina diinorplia, were recorded 

 as new to Britain. Schlnmberayer's unique genus and species, 

 Hindci-ina briigesii, was recorded from the Eocene clays. 

 Also the first fossil records of Biilimina snbtercs and 

 Discorbitia polystoinclloidcs. Tlie new species recorded 

 were Piilviniilina haliotidca H. .\. and E., and Xonionina 

 quadriloculafa, H.A. and E. Specimens of these were 

 exhibited under microscopes during the meeting. 



Mr. Lees Curties described a new dark-ground illuminator 

 which he had made to the instructions of .Mr. l-~. AL Nelson, 

 and which was so constructed as to work with slips ranging 

 from 0-8 to 1-2 millimetres in thickness, and which gave a 

 perfectly dark field with a Zeiss apochromatic four millimetres 

 lens of 0-95 N.A. The illuminator was provided with a fixed 

 central stop, and also with a slot for utilising the apparatus as 

 an oblique illuminator. A small dot placed on the front lens 

 served for the purpose of centring the condenser to the 

 optical axis. 



SOME WORKS REFERRING TO RED-SNOW.— Mr. 

 James Murray has kindly prepared the following short 

 bibliography on the subject of his paper (see " Knowledge." 

 page 109) ; it will be of use to those readers who are desirous 

 of carrying fuither the subject of " Red-Snow " and its 

 occurrence. 



Agardh. — Systcina Algariiin. \S1\. 

 .'\ristoteles. — Historia An iiiuiliiiin. V. \Z. 



Charcot. — Rapports prcHininaircs siir Ics Travaiix executes 

 dans i'Aiitarctiqiic. .^cad. des Sci. Page 76. Paris, 

 1910. 



Chladni.— Fi-xtT Mcfeorc. Pages 359-390. 1S19. 



Darwin, C. — Journal of Researches. Page 311. London, 

 1845. 



Ehrenberg, C. G. — .Mikr. Lebcn d. Alpeii n. Gletscher d. 

 Schweiz. Ber. X'erh. K. Akad. Berl. 1849. 



Hooker, J. D. — Himalayan Journals. 



Kerner and OUver. — TIic Xatiiral History o/ Plants. WA. 

 I. Pages 38. 54_'. Vol.11. Pages 627-631. etc. 1895. 



Lagerheim. G. de. — Die Sclineetiora des Pichincha. Bcr. 

 " dcutsch. Bot. Ges. X. Pages 517-534. 1892. 



Murray. J. — .Antarctic Rotifera : Brit. .Antarct. Exped.. 



1907-9. Sci. Reports. Vol 1. Page 41. 1910. 

 Ross. Sir John. — Voyafie of Discovery, for the purpose of 



exploring Baffin's Bay. 1819. 

 Schmarda, L. — Klcine Beitrdge ziir Xaturgeschichte der 



Infusoricn. Wien. 1846. 

 Shutllcwortli. R. J. — I. a inatiire coloraiite de la Seige 



Rouge. Bibl. L'iii\. de Geneve. T Is. Pa,L;e 383. 



1840. 

 Vogt, C. — Xotiee siir les .-\ni nuilciiles de la Xeige Rouge. 



Bibl. Univ. de (iencve. Pages 80-86, April. 1841. 



(JUEKETT MICROSCOPICAL CLUB.— Febnwry 28th, 

 1911. — Mr. D. J. Scourfield, V.Z.S.. F.R.M.S.. Vice-President, 

 haxing taken the chair, the President delivered his annual 

 address dealing this year with " Some Problems of F^ volution 

 in the Simplest Forms of Life." 



Taking, first, the visible world of living creatures, no deep 

 reflection or analysis is required to grasp the fact that it does 

 not constitute a chaos of isolated and unconnected forms, but 

 is capable of being classified into greater or lesser categories. 

 The first and most obvious division is into animals and plants. 



But between the categories of greatest and least extent there 

 are a number of intervening divisions, with regard to which 

 the scientific and the non-scientific public are hopelessly at 

 variance. The same is inevitably true in any branch of 

 knowledge dealing with a variety of concrete objects, simply 

 because the mind devoted to the study of any particular 

 set of things, animate or inanimate, soon becomes perforce 

 acquainted with so many more than ever come within the ken 

 of the casual observer, that in order to arrange them in an 

 orderly and intelligible system of classification, it is necessary 

 to draw distinctions and institute comparisons which are never 

 dreamt of in the philosophy of the mind occupied with other 

 pursuits. 



Professor Minchin tlicn proceeded to review various systems 

 of classification popularly recognised, as, for instance, the 

 separation of \ertebrates into two main groups, one with 

 paired limbs, as in fishes, and the other in which the paired 

 limbs are pentadactyle in type. Then, again, animals may be 

 divided by their habitat into terrestrial, aquatic and aerial. 

 But to all these systems we at once find exceptions. Many 

 perfectly logical classifications are possible, but only one that 

 is perfectly natural, and that one, very often, is not perfectly 

 logical. It is now abundantly clear that natural groups can 

 seldom, if ever, be defined by precise and rigorous verbal 

 definitions. All that can be done is to construct for each 

 group a more or less ideal and imaginary type of organism, 

 possessing certain characters, none of which must be regarded 

 as fixed or invariable. If we must have verbal definitions of 

 groups, then logic requires the insertion of the word 

 "typically" before each character ascribed to them. 



In dealing with the Protista, the President considered 

 that there are two well-marked types recognisable in these 

 organisms, one more primitive and older in evolution, the other 

 higher, and leading on to the ordinary plants and animals. 

 The difference between these two types depends on the con- 

 dition under which that peculiar substance occurs for which 

 we may use, in quite a general sense, the term chromatin. In 

 every cell of animal or plant,' and probably in e\erj- Protist 



