December. 1910. 



KNOWLEDGE. 



485 



MICROSCOPY 



By A. W. Sheppard. F.R.M.S.. 



xc-ith tlic assistance of the folloic'tiig nitcroscopists : — 



Arihl'r C. Bankield. 

 James Elrton. 



The Rev. E. W. Howell, .M..A. 

 Charles H. Caffvn. 



.\rthur Earland. K.R.-M.S. 

 Richard T. Lewis, F.R.M.S. 

 Chas. F. Rocsselet, F.R..M.S. 

 D. J. ScouKFiELD, FZ.S., F.R.M.S. 



C. D. Scar, F.R.M.S 



RED WATER-BLOOM iLaiiiprocystis rosco-persiciiia 

 Schroeter). — Owing to the kindness of a fellow member of 

 the Quekett Microscopical Club. I have received some 

 specimens of an interesting organism which he collected from 

 a pond at Hendon. It was chiefly found attached to water- 

 plants along the margin, but some examples were free. To 

 the naked eye it appeared as small irregular sphaeroidal masses 

 of a fine purple or rose-pink colour. Under the microscope 

 these were seen to consist of balls and lobes of \ery various 

 shapes and sizes, which were frequently joined together in a 

 net-like manner. They were hollow and were formed by a thin 

 membranous laver of extremely minute round bodies, which 



Figure 1. Red Water Bloom. 



often contained opaque granules. The larger compound 

 bodies were sometimes as much as 1-mm. in length and 

 breadth, while the component round jelly-like dots measured 

 from 2 to 3 M. The organism was identified as one of the 

 sulphur bacteria, not verj- uncommon, though probably not 

 often recognized, and the cause of red water-bloom. Like 

 many of its relatives, it has been described under various 

 names by different observers. There are at least eight 

 s\nonyms for it. Sir Ray Lankester, many years ago, 

 found it in some jars containing putrescent remains of animals 

 and plants, which had been undisturbed for a time in his 

 laboratory. He named it Bacterium rubesccns, and par- 

 ticularlv noted its brilliant colour. (See Quart. Joitrii. Micr. 

 Sci., 1873. N.S. Vol. .xiii.). Dr. Cooke. in~' Brit. F. W. Algae," 

 refers, there is little doubt, to the same organism, as 

 Pleiirococciis roseo-persicinus (Rabh.) with the remaik that 

 it is " certainly not a good Pleurococcus." It is the 

 Protococciis roseo-persicinus of Kiitzing, and Clathrocystis 

 roseo-persiciita (Cohn). There is considerable reason for 

 classing it with Clathrocystis. as a reticulate form is very 

 common in some stages of growth, but there is no doubt it 

 does not belong to the algae. It is Reggiatoa roseo-persicina 

 (Zopf.t, and under this name is recorded as occurring in 

 extraordinary abundance in a farm pond at Hampstead. The 

 water was deeply coloured, and weeds and debris entirely 

 covered by it. (See Science Gossip. N.S. \'ol. vii, No. S3, 

 .•\pl. 1901.) But Grove, in his "Synopsis of the Bacteria," 

 calls it Cohnia roseo-persicina in honour of Professor 

 Dr, F, Cohn, of Breslau, and gives an excellent description, 

 from which the following is taken. Cells roundish, in a 

 simple peripheral layer, forming hollow, round or afterwards 

 irregular, bladders or vesicles, which finally are reticulately 

 pierced. Multiplication of the cells by repeated bipartition : 

 of the families by the separation of daughter colonies. \'ary- 

 ing from rose to purple-red. The cells form at first solid 



families ; later the families become larger, globular or ovoid, 



and finally irregular bodies which are hollow- (Figure 1, A). 



These are often torn or perforated ; in the end they present 



an elegant network (Figure 1. Bi, which at last breaks up into 



rags and tatters. The species is distinguished by its red 



colouring matter, w hich is designated " bacterio-purpurin " and 



is insoluble in water and cold alcohol. Each individual cell 



(Figure 1, C), is surrounded by a dense almost cartilaginous 



membrane ; its contents are at first homogeneous, but as it 



grows older one or more dark granules can be observed in it, 



which are found to be nothing but pure sulphur. Tlie 



figures are front my oic'n specimens, but someichat 



diagrammatic. , ,, 



J.B. 



CANNIBALISTIC TENDENCIES IN ROTIFERS.— 

 The food of Rotifers consists mostly of small flagellate 

 infusoria, algae, desmids. diatoms, spores of fungi and even 

 bacteria. Some species have learned to pierce the cells of 

 filamentous and larger aquatic algae in order to extract the 

 protoplasm they contain. Another section of Rotifera is 

 essentially carnivorous, and these attack dead or living 

 creatures. such as vorticella. whilst others (such a.sAsplaiichna) 

 feed on li\ing Rotifera. which they swallow whole. Each 

 species has jaws, contained in a masta.x. suitable for its special 

 food and mode of life, for either crushing, tearing, piercing, 

 holding or sucking, and frequently several of these functions 

 are combined in one mastax. 



Though the food of Rotifera is so varied it is rare that one 

 meets with a species which has a preference for its own 

 nearest relations. Sue h an one. however, is Ploeso m a h u dson / , 

 a species found in some abundance at a recent Quekett Club 

 Excursion to the East London Waterworks, at Tottenham. 

 The species was first discovered by Dr. Imhof about 1888, in 

 Switzerland, and shortly afterwards appeared in several 



Figure 2. Cannibalistic Rotifers. 



places in Germany and Galicia. Some 16 years ago Mr. John 

 Hood found it in the reservoirs of the Dundee Water Supply, 

 and used to send me specimens from time to time, but with 

 the invariable result that onl.\- very few individuals sur\i\ed 

 the journey, whilst the dead remains of the others could be 

 seen at the bottom of the little bottle. On my informing 

 Mr. Hood of this he called the Rotifer " a most atrocious 

 cannibal." for he had already observed how it attacked and 

 de\oured its own kin. 



Of all Rotifera this is the most vigorous swimmer; it 

 rashes through the water at great speed, snapping at any other 

 Rotifer that comes in its way. carrying it in its mouth and 

 devouring it without a moment's pause. It is not at all 

 particular as to whether its victim is a.Synchaeta or its own 

 sister or cousin. 



The integument of this Plocsoma is tough and leathery: it 

 has a broad somewhat flattened head, and a long stout foot 

 issuing from near the middle of the \entral side of the body. 

 The attacking individual snaps at and holds on to its victim like 

 a bull-dog. and proceeds to pierce the skin by means of that 

 part of the mastax called " incus," .after which the muscular 



