82 



HARDWICKE'S SCIENCE-GOSSIP. 



this organism has a true mouth for the reception of 

 food. Sometimes it stops swimming and rapidly 

 changes its form and becomes irregular in outline 

 (Fig. 43 b) while the long flagellum is seen to wave 

 about in the water. The ectosarc seems eminently 

 contractile, like that of the Amceba or Euglena. We 

 shall see that the contractility of the ectosarc varies 

 greatly in the different species of Infusoria, in 

 Paramcecium it is not contractile, though not very 

 resistant to objects that may be pressed against it, 

 while in Coleps the ectosarc is cuticular. 



The resemblance of Astasia to Euglena, presently 

 to be described, is very striking indeed. Ehrenberg 

 and Dujardin classed both forms together into the 

 same family. 



2. Euglena viridis is by many considered a plant, 

 by others an animal. Like a plant, it contains green 

 chlorophyll, and it may be noted that it bears a 

 general resemblance to the free-swimming Zoospores 

 of certain Algae. 



Its length varies from the thousandth to the two- 

 hundred-and-fiftieth of an inch. It is exceedingly 

 common in pond-water and may often be found in 

 great multitudes in the green water found at the 

 bottom of manure heaps. When fully extended, it is 

 seen to be somewhat spindle-shaped; one end is clear, 

 and contains a minute red angular body, the red 

 ocellus or eye-spot. It is difficult to say what is the 

 function of this bright particle, but it is found in the 

 Zoospores, as well as in many of the free-swimming 

 green Flagellata which may be grouped collectively 

 as Flagellate Algce. The rest of the protoplasmic 

 cell contains chlorophyll corpuscles. This green 

 colouring-matter is not diffused throughout the 

 general substance, but collected in little green masses 

 of protoplasm (chlorophyll corpuscles) as in the 

 higher plants. In the centre of the cell there is 

 sometimes a large round body, resembling in appear- 

 ance the pyrenoids seen in Desmids, Zygnemaceae, 

 and also probably in the Zoospores. Although it 

 occupies the centre of the cell it seems too well- 

 defined for a nucleus, and if it be so, is green 

 chlorophyll-containing. 



The anterior end is slightly notched, the posterior 

 end is prolonged into a tail and is clear and colourless. 

 Sometimes the protoplasm is stuffed with granules 

 which look like starch grains but do not stain blue, 

 but a deep brown, with iodine. The motile filament, 

 •springing from the notch before mentioned, is longer 

 than the body, and furnished with a small knob at 

 the free extremity. 



Euglena is seen to frequently change its form in a 

 manner somewhat similar to Astasia, only there may 

 be noted this difference : in Astasia the anterior 

 extremity participates less than the remaining proto- 

 plasm in this change, while in Euglena the anterior 

 and posterior ends both seem the less motile. Unlike 

 many other Flagellate Alga;, Euglena viridis has no 

 cell- wall as have its allies Phacus and Euglena pyrum 



There are other allies of Euglena viridis which will 

 only be briefly mentioned ; among these are Euglena 

 acus, E. pyrum, and E. longicauda. 



3. Euglena longicauda, sometimes called Phacus 

 longicauda, is of somewhat larger size than the pre- 

 ceding. In the " Micrographic Dictionary" it is 

 said to be from the one-hundred-and-eightieth to the 

 one-hundred-and-twentieth of an inch. Its move- 

 ments are slow, and it has a peculiar habit of twisting 

 its body. The ectosarc is marked obliquely with 

 lines resembling the myophan striae of the Ciliata. 



4. Euglena pyrum, unlike the two other Euglena, 

 is furnished with a firm cell-wall formed from the 

 ectosarc. This case is sometimes found empty, and 

 then delicate spiral markings can be seen. In size it 

 may vary from the thousandth to the eight-hundred- 

 and fiftieth of an inch, so that it is much smaller than 

 E. viridis. 



5. Phacus pleuronotes is about the six-hundredth of 

 an inch in length. In one aspect it is broad, roughly 

 oval, but broader near the base, in another view it is 

 thin and narrow, so that it may be described as plate- 

 like. It rolls lazily round on its long axis as it swims, 

 presenting alternately the broad and narrow aspect to 

 the observer. The anterior part is cleft, and from 

 this a delicate flagellum arises. The posterior end 

 is prolonged into an obliquely directed tail. The 

 cell-wall is marked with striae, the strongest of which 

 radiate from the cleft to the tail. 



In the interior there is an eye-spot, situated near 

 the origin of the flagellum. There are usually two 

 vacuoles, which do not appear to be contractile, the 

 smaller of which is near the red ocellus. Chlorophyll 

 corpuscles more or less fill the rest of the interior. 

 Sometimes there are one or two oval, colourless, 

 highly-refractive bodies with concentric markings, 

 and which do not stain with iodine. 



The two little organisms Doxococeus and Chaeto- 

 glena are often found together in pond-water. 



6. Doxococeus ruber, something bigger than the 

 two-thousandth of an inch in diameter, is round and 

 rolls over and over as it swims. The thick cell- 

 wall is of a reddish-brown hue and hides the proto- 

 plasm with its green corpuscles. Through a hole in 

 the case surrounded by a ring the flagellum protudes. 

 By the pressure of the cover-glass we may easily 

 crush the brittle cell-wall, and in this way expose the 

 protoplasm with its corpuscles and red eye-spot. 



TThe other figures will appear in next paper. — 

 Ed.] 



BRITISH POISONOUS PLANTS. 



CONSIDERING the extent of our native flora, 

 we are happily exempt from many poisonous 

 species, and those plants that are known as injurious 

 are either not very common, or are easily recognised. 

 In our immediate neighbourhood, with the exception 

 of some scattered plants of Solatium dulcamara, 



