KNOW I.I |)C,| 



FiGUKic 222. \'e 



till- same diatom taken at coii- 

 scciitivL- foci fniiu the white dot 

 down to the l)lack dot imaf,'f- 



KICKNSCHWAK/.— In photo- 

 Kiaphing sections, dne contrast 

 may be obtained by the screen 

 and bathed plate method. Hnt, 

 where it is possible, I prefer to 

 stain the specimen for this par- 

 ticular purpose, and use ordinar\ 

 process plates with the Holt Conn 

 developer. Kernschwarz. recom- 

 mended long ago for this purpose 

 by Holies Lee. is an excellent 

 stain for such specimens. It is 

 especially good when one desires 

 to show sharply and distinctl>- 

 the general appearance of ii 

 section. Figure 221 is a section 

 through the thorax of a youn.i; 

 rat done by this method ; lungs, 

 oesophagus and vagi, aorta, 

 thoracic duct and pleurae will 

 be readily recognised. Carmine 

 preparations are much less satis 

 factory ; one is shown in Figure 

 2221 vermiform appendix, injected). 

 E. W. B. 

 AKRHENURUS INSUL- 

 AXUS KOEN.— In .'Vugust, 1S94, 

 1 found in a small pond in the 

 Warren, Folkestone, a beautiful 

 dark red female .Vrrhenm-us. 

 which I could not identify. It is 

 always very difficult to identify 

 a species of .Arrhenurus from the female as the females are so 

 much a hke With the males it is comparatively easv because 

 they all exhibit a distmct structure from one another. In 

 1896 I again visited the same pond and did all I could to fmd 

 a male or at least more females, but I had no luck I can 

 only conclude that during the two years the pond had been 

 dried up and in that case all the Hydrachnids that were there 

 111 .'^94 had died out, so when I published mv list of Water 

 Mites found in the Warren in 1894 and 1896 I mentioned 

 that 1 had found one particular female 

 -Arrhenurus I could not name for 

 want of the male. (See Figure 2 'J ) 

 In October, 1899. Mr. HalbertV of 

 Dublin, sent me a female he had 

 found ill Ireland, which on examina- 

 tion turned out to be the same species, 

 only this specimen was not quite fully 

 developed. Here again the male was 

 not taken, so it still went unrecorded 

 and unnamed. 



Ill 1911, Dr, F. Koenike, of Brenuii. 

 found the same species in Xoiih 

 Germain-, but curiously enough ihe 

 male was still wanting. Di-. Koenike 

 is one of the greatest authorities we 

 have on the Hydrachnidae, and was 

 sure it had never been named, so 

 named it at once as Arrhennnts 

 insiilaitiis. There is always a certain 

 amount of risk in this because we 

 have several male .'Vrrhenurus which 

 have been named, but at present do 

 not know the proper females to place 

 with them. This particular female, 

 however, although of the usual shape, 

 has very unusual genital plates, as 

 can be seen in Figure 224. 



I take this opportunity to place the 

 name Arrlieiiiinis insidanus Koen. 



on the British list. Hut the object of FiGl'KI-: 224. The 

 this note is more with the idea of specimen seen in 



nnilorui .-ippcndix. injected. 



xs^5^^ 



I 



FlGUKi; 223. 

 \'ontial 



.4 ;•/■/; c 

 Hirface 



M\v. 1912. 



indufiug some of our pond hunters 

 during the coming season to find 

 the male, which, to judge by the 

 size of the female and its beau- 

 tiful colouring, must be a very 

 handsome creature. 



CiiAs. D. Soar. 



.\ i'AK.vsith: alg.a. — I 



have received through a friend 

 at the Ouekett .Microscopical 

 Club some portions of leaves of 

 Arisarum viilfiarc attacked by 

 the parasitic alga Phyllosiplioti 

 iirisari. On holding a piece 

 of the dried leaf up to the 

 light, it is noticed that the 

 ihlorophyllj in the worst cases, 

 is destroyed in the neighbour- 

 iiood of the alga, leaving a 

 colorless and partially trans- 

 parent spot, in which, after 

 preparation and examination 

 under the microscope, it is 

 evident that the internal struc- 

 ture is broken up. little indeed 

 remaining but the upper and lower 

 cuticles — even they being in a 

 more or less disorganized 

 condition — and the vascular 

 bundles. Between the cuticles 

 the filaments of the alga can 

 be seen ramifying, radiating 

 from what is probably the centre 

 of infection. It is noticeable 

 that where a vascular bundle crosses the leaf, the filaments 

 are checked in their progress (see Figure 225 A), They 

 proceed chiefly in the intercellular spaces of the spongy paren- 

 chyma, absorbing the protoplasm and chlorophyll on the way, 

 at last destroying the cells also. The alga consists of much 

 branched tubes, from about 25 to -tOm diameter: they have 

 firm walls and are filled with protoplasm, in which are very 

 numerous small oval green chloropl.ists about 2\hi in their 

 longest di.iiiu'ter: many nuclei are present. From the fact 

 that the plant possesses chlorophyll 

 of its own in abundance, it may be 

 concluded that it is only partially 

 parasitic, but it no doubt obtains its 

 water, mineral and nitrogenous ele- 

 ments from the host, although most 

 likely it is able to fix COj for its 

 ret|iiiremeiits. The characteristic fea- 

 ture is that, although of very con- 

 siderable length the tubes have no 

 cross walls ; each has a continuous 

 cavity for its whole length, and may 

 be looked upon, therefore, as one 

 cell only, and the plant notwith- 

 standing its size is unicellular. This 

 peculiarity has caused it to be classed 

 with the Siphoncac. The very com- 

 mon alga Vauchcria belonging to 

 the order has the same feature ;ind 

 indeed Pliyllosipliun closely resembles 

 a delicate specimen of Vaitchcria. 

 Just as in that plant too, owing to 

 the absence of dividing walls, if a 

 filament is cut or injured, the contents 

 escape, leaving nothing but the empty 

 tubular wall, of which several ex- 

 amples may be seen in the figure. 

 I have not been able to find out 

 anything respecting its reproduction, 

 and in my specimens, of course some- 

 what suttering from the drying, there 

 is no sign of anything of the kind. 





< iiisii/tiiius Koen. 

 female X 19. 



