Deckmber, 1911. 



KNOWLEDGE. 



481 



Figure 1. 



which either the micronuclei were not ripe for mitosis, or the 

 stimulus was not sufficiently intense to evoUe a division. 



Durint; normal fission when all the micronuclei present 

 divide, there is a general formation of new parts, quite 

 comparable with the localised acti%ity in regeneration and 

 accompanied, it is natural to suppose, with much the same 

 condition of the cytoplasm. The mitoses occurring normally 

 and those taking place during regeneration, can thus be 

 brought under one point of view. 



EUGLEN A EHR. — .Although such a " connnon object" 

 as sometimes to be quite an inconvenience to the microscopist, 

 Euglcna viridis (Figure 1) has many points of interest which 

 will repay rather more attention than is usually accorded to 

 them. As with not a few other micro-organisms, in the past 

 there has been much dis- 

 cussion as to whether it 

 should be classed as an 

 animal or as a plant. 

 The modern view is that 

 it partakes of the nature 

 of both and may best be ;■ 

 described as a plant- L ' 

 animal. Its possession of ' K, 

 a mouth, and the ingestion 

 of solid food, and its 

 general activity entitle it 

 to be looked upon as an 

 animal ; while its green 

 colour, which is undoubt- 

 edly due to the presence 

 of chlorophyll of the 

 same character with that 

 of plants, and the fact 

 that it appears possible 

 for it to exist without taking in food by the mouth, endorse its 

 claims to be considered as belonging to the vegetable kingdom. 

 Recently a small book under the name of '' Flant-animals, 

 a study in symbiosis " was published, describing two small 

 worms (Convoluta) which display the same characteristics 

 in a marked degree. The facts ascertained respecting 

 these and the exhaustive experiments made on them 

 prove conclusively that there are aquatic organisms, 

 which, though unquestionably animals, yet owing to the 

 inclusion of chlorophyll within tliem are able to, and 

 actually do, obtain the carbon elements of their food, at least 

 during a portion of their life, from the carbon dioxide 

 dissolved in the water. The extent to which this capacity is 

 possessed and exercised differs in various cases, but Eiiglena 

 viridis certainly takes advantage of its endowment in this 

 respect and so may be looked upon as a plant-animal. It has 

 been suggested that the creature takes in nourishment during 

 daylight as a plant by means of its chlorophyll, during the 

 darkness feeding as an animal, but perhaps this idea rather 

 exaggerates its voracity. It is not possible to make oat the 

 mouth and flagellum while the animal is swimming, but the 

 careful application of a little iodine will kill it and bring them 

 into view. The mouth is a funnel-shaped depression in the 

 forward end — only capable of receiving very small particles — 

 and from it springs the long, and during active life, swiftly 

 moving flagellum (Figure 2a). The body is covered with a 

 delicate cuticle, not sufficiently firm to prevent it readily 

 changing shape; that represented at Figure 2b, is frequently 

 assumed. The protoplasm is granular and the chlorophyll 

 seems to be diffused in it, not collected into definite " chloro- 

 plasts." Many partially transparent bodies of considerable 

 size are usually present ; they resemble starch grains, but the 

 substance composing them is known as paraiuyhini. and 

 though having the same chemical composition as starch, is 

 not coloured blue by iodine. A nucleus is present and near 

 the usually distinct red '' eye spot " a contractile vacuole. 

 For the purpose of multiplication, towards autumn, or at any 

 time on the occurrence of unfavourable conditions. Englciia 

 may assume the encysted state. The body becomes spherical 

 and a wall of cellulose tjeffery Parker) is secreted round it. If 

 the animals are present in great numbers — as is frequently 



Figure 2. 



the case — they adhere and form a kind of pellicle on 

 the surface of the water. Blown by the wind, or 

 moved by any object, this does not readily break up, but 

 will crease and fold, just as the scum on boiling milk does. 

 Later the animals may resume their active state, and the 

 cells which contained them (at first circular, but aftervv.ards, 

 owing to pressure and mo\ement, angular and mis-shapeni are 

 left adhering together, and have exactly the appearance of a 

 cellular membrane (Figure 1). This persists for some time, 

 and various floating a<iuatic organisms make it their home. It 

 has been mistaken for, and described as, some kind of alga. 

 During the past summer this object has often been noticeable 

 on the surface of ponds as a brownish delicate film. While 

 resting encysted the individuals may undergo division into 

 two or four smaller specimens, but of the same shape as the 



adults, so that on emer- 

 gence their numbers are 

 greatly increased. Figure 

 2c, "An interesting local 

 variety of Eiiglena 

 I'iridis. has been des- 

 cribed by Mr. M. H. 

 Robson, of Newcastle- 

 on-Tyne. in Science 

 Gossip, October. 1879, 

 in which the distal ex- 

 tremity of the flagellum 

 piesents an inflated knob- 

 ike aspect." Figure 2d : 

 The same singular variety 

 has recently been recog- 

 nised in some ponds near 

 London. 



Figure 1 is from a 

 specimen which lasted 

 several weeks in a saucer of water after being brought from 

 a pond. The membrane is represented on the same scale as 

 the two animals above. Figure 2 is from Saville Kent's 

 Infusoria, a and c highly magnified. , u,..,-,. ,,. 



AMPHIDINIUM OPERCULATVM CLAP AND 

 LACH. — In the Journal of the Linnean Society, \ol. XXXII, 

 pages 71-75, Professor W. A. Herdman, F.R.S.. describes the 

 occurrence of this little peridinian in vast quantities in Port 

 Erin Bay (Isle of Man). The hollows of the ripple-marks and 

 other slight depressions formed by the water draining off the 

 beach were occupied and outlined by a greenish-brown deposit 

 which in places extended on to the level, so as to discolour 

 patches of the sand. Here the deposit remained more or less 

 for a month, waxing and waning, sometimes increasing in the 

 tide, say, roughly ten-fold, and at other times apparently 

 disappearing for a day or two and then reappearing either on 

 the same part of the beach, or it might be a few hundred 

 yards away. At one time it coloured a continuous stretch of 

 sand about fifty yards long by five yards in breadth just below 

 high-water mark, and was noticeable for some distance away. 

 On examination the deposit was found to consist of vast 

 numbers of A. opcrciilatnni. This peridinian was first 

 described bv Claparede and Lachmann. in 1858. from 

 specimens obtained in some few places in Norway, and 

 according to a recent authority is found occurring in brackish 

 water on the North Coast of Europe, but has not been 

 previously recorded for the British area. It was first 

 obser\ed at Port Erin early in the year, but later brown 

 patches of similar appearance were again observed on the 

 sand ; on examination these were found to consist of vast 

 numbers of a golden-yellow naviculoid Diatom. The 

 Amphidinium had disappeared, but re-appeared in abundance 

 by September. 



Under observation A. opcrciilatnni swims about freely, 

 but soon comes to rest by attaching itself to a sand-grain. It 

 is positively heliotropic and collects in quantity on that side of 

 the dish which is turned towards the light. Multiplication b>- 

 fission was frequently observed. Its greatest diameter is 

 0-()5 millimetres. 



