MICROSCOPE. 



669 



an inch, and their diameter is from l-20th to 1 100th 

 of their length: they require considerable magnify- 

 ing power, and large angular aperture, to distinguish 

 their structure." " I find, on reference to my notes, 

 made at different times, that it was not until after 

 I had examined them repeatedly, I became satisfied 

 of their animal vitality. They generally reside at 

 the bottom of ponds, but after rain are met with 

 near the surface, giving the water a green tint ; in 

 such cases they are found separate, the agitation of 

 the water having broken the clusters." 



Cyclidium " This genus is composed of animal- 

 cules of a flat, round, or oval form, without any 

 apparent cilia. Like some others, they are so very 

 diaphanous that the most delicately finished en- 

 gravings of them, afford but a faint idea of their 

 exquisitely brilliant, crystal-like appearance, when 

 viewed under a good achromatic microscope of 

 large angular aperture." 



Fig. 62. The Azure Cyclidium." Is of a flat 

 oval form. In its usual condition it is pellucid, 

 but when fed with colouring matter, dark spots 

 may be seen, as in the drawing. In swimming it 

 sometimes rotates, and exhibits its narrow side to 

 view ; and if the water be filled with opaque par- 

 ticles, a current may be perceived towards the front 

 of it, indicating the presence of cilia, which, how- 

 ever, can only be seen when the animal is expir- 

 ing. These creatures propagate by division, during 

 the progress of which they alter their form. They 

 require a magnifying power from 400 to 800 times 

 to view them distinctly. Length, l-1400th to 

 UlSOOth of an inch." 



Paramaecium. " The animalcules included in 

 this genus, are membraneous, long, and rather flat. 

 Ehrenberg supposes these and the kolpoda to be 

 the same as the monads, and cyclidia, at a more 

 advanced stage of their growth." 



Fig. 63. Paramaecium chrysalis. " These inter- 

 esting creatures appear like milk white specks to the 

 naked eye. They are soft, and yield to the pres- I 

 sure of any hard substance they may come in con- 

 tact with. The body is long, and in some positions 

 the cuticle appears to have a diagonal fold, as shown 

 in the figure. The mouth aperture is situated on 

 the inferior side, near the middle, and in some 

 views it appears like a papillary projection. In 

 good microscopes the body is seen covered with 

 longitudinal rows of hair ; by means of these, the 

 creature is enabled to produce a current in the 

 water towards its mouth. They propagate by 

 transverse division. These animalcules are well 

 adapted for exhibiting the structure of the alimen- 

 tary organs, as they are of sufficient magnitude to 

 render the sacs clearly perceptible, when filled with 

 coloured particles. On the introduction of indigo 

 into the water they are greatly agitated ; in a few 

 minutes, however, they are quiet, and the digestive 

 sacs become coloured, as in the drawing, when 

 from 100 to 200 may be enumerated. Length, 

 l-85th to l-200th of an inch." 



Kolpoda " This genus is thus defined by Miil- 

 ler: 'an invisible, very simple, pellucid, flat, 

 crooked animalcule.' They vary much in external 

 form." 



Fig. 64. The Cuckoo Kolpoda, or common Bosom 

 animalcule. " Its general contour has some resem- 

 blance to a bean ; and if we suppose the two con- 

 vex lobes or the front side equal, and do not per- 

 ceive the proboscis, which indeed is seen with diffi- 

 culty, we shall distinguish some likeness to the 

 bosom ; from which similitude it has received its 



name. The mouth, which is lighter tinted than 

 the surrounding parts, is situated in the hollow be- 

 tween the upper lobe and the proboscis, and marked 

 by a cross, while the termination of the alimentary 

 canal is in the cavity immediately below the pro- 

 boscis. The margin of the two lobes is furnished 

 with a row of delicate cilia, only observable under 

 favourable illumination. These cilia, by producing 

 a current in the water towards the mouth, perform 

 the same important office as members in some of 

 the mammalia; as the current brings all the parti- 

 cles of matter in the water to the mouth in regular 

 succession." "By feeding them on vegetable 

 colouring matter, the polygastric form of their di- 

 gestive organs is readily distinguished." " Length 

 of full grown specimens, l-280th of an inch. They 

 are found in various vegetable infusions, and 

 especially in those of hay which have been kept a 

 considerable time." 



Gonium " The animalcules of this genus are 



in clusters ; they are propagated by several incisions 

 across the body of the parent, dividing it into a 

 number of symmetrical forms. When observed 

 singly, most of the species resemble the volvox. 

 The structure of their digestive organs is not 

 known. Muller defines this genus as composed 

 of 'invisible, simple, smooth, angular animal- 

 cules.'" 



Fig. 69. The Breast-plate Gonium "It con- 

 sists of sixteen spherical bodies, disposed regularly 

 in a quadrangular form, like the jewels in the 

 breast-plate of the Jewish high priest. They are 

 all arranged in the same plane ; the four centre 

 ones are generally larger than those which surround 

 them ; and the diameters of the three smaller balk 

 are only equal to the two larger centre ones to 

 which they are attached ; the external corners are 

 consequently vacant." " The diameters of the 

 clusters vary from l-350th to l-200th of an inch." 

 " They are found near the surface of clear water, 

 and often along with the Cercaria viridis. A 

 magnifying power of 200 is sufficient for their ex- 

 amination." 



Bursaria. " ' A simple, hollow, membraneous 

 animalcule,' which takes its name from its bag or 

 purse-like form. Ehrenberg has only notjced one 

 species, and has not decided as to the situation of 

 the genus." 



Fig. 60. The little swallow -like Bursaria "The 

 form of this animalcule, by a little effort of im- 

 agination, may be compared to a bird, and its 

 movements appear like the flight of the swallow : 

 hence its name." "It is found in stagnant water. 



Cercaria. " An ' invisible, pellucid animalcule, 

 with a tail.' If we consider the internal organiz- 

 ation of this genus, it comprehends a very wide 

 range ; indeed, the different species vary so much 

 that it is difficult to give a general definition of 

 their characters with any degree of accuracy." 



Fig. 59. The Green Cercaria " This is a highly 

 interesting creature : the bright green colour of its 

 body ; its diaphanous extremities ; its well-defined 

 orange brown eye ; and the numerous transforma- 

 tions of its form, render it a very entertaining ob- 

 ject for the microscope ; in addition to which it is 

 easily procured, and managed with great facility." 

 " The length of the specimens which I have ex- 

 amined was about l-350th of an inch : Ehrenberg 

 gives 1 -280th as their length." " The magnifying 

 power best adapted for viewing them, is from 300 

 to 500 times, in an achromatic." 

 Leucophrys. " Diaphanous, ciliated animalcules." 



