668 



MICROSCOPE. 



and curious: indeed there uio few in the examina- 

 tion of which I have been more delighted. This 

 gratification arises, not so much from any com- 

 plexity in their organization, which in comparison 

 with the Brachionus, and some of the Vorticella, is 

 more simple, hut from the great power they possess 

 of dilating their bodies; and their motions being 

 slow, the observer is enabled to examine their 

 changes of form distinctly. Their generic charac- 

 ter, according to Miiller, is, ' that their form is ! 

 changeable, extending variable feet-like processes 

 at pleasure.'" 



Fig. 66. The Melting Proteus " The drawing of 



this animalcule I took from a specimen found in 

 some water containing duck-weed (lemna major), 

 in the month of March. They are very scarce. 

 Miiller states he only saw them twice. Their diame- 

 ters vary from l-600th to 1 -300th of an inch." 



Volvox. " The animalcules belonging to this 

 genus are of a globular form, and revolve in the 

 water. Some of the species are so large as to be 

 discerned by unassisted vision, while others are 

 very diminutive. Ehrenbreg has not demonstrated 

 their digestive organization ; but in a note to his 

 table, conceives they ought to follow the monads. 

 In this genus is included that beautiful animalcule, 

 called the Volvox globater, which forms so interest- 

 ing a spectacle in the solar and gas microscopes." 



Fig. 67. The Vegetable Volvox "This ani- 

 malcule is rather scarce. Its most interesting char- 

 acter is the short time which it requires in arriving 

 at maturity, and undergoing all its changes. In the 

 space of half an hour, when fed with an infusion of 

 indigo, a single globule may be observed to emerge 

 from a naked branch, increase in size, and divide 

 into a cluster of smaller ones ; these increase also, 

 and after revolving, and bringing a current of food 

 towards them, finally separate, and swim away, 

 each of the young ones commencing a similar 

 course." 



" It consists of several opaque branches : at the 

 termination of each is a small congeries of egg- 

 shaped transparent bodies. Miiller, who seems to 

 have only seen them once, mistook them for a 

 vegetable production, until he observed the clusters 

 to separate from the branch, and swim about at 

 pleasure." 



" These animalcules produce a rapid current of 

 water towards them as indicated by the arrow in 

 the figure ; and if supplied with plenty of coloured 

 food, as indigo, they will not only assume the 

 colour of the particles, but may be seen to increase 

 in size, under the eye of the observer. When the 

 cluster is fully developed, it breaks off, and swims 

 away, revolving as it proceeds. After roving 

 about for a few minutes in search of a proper nidus 

 to attach itself to, it spins a very delicate thread, 

 like a spider's web, one end of which it fixes to 

 the substance it has selected : this filament, when 

 drawn out to the proper length, increases in size, 

 and assumes the deep blue colour of the indigo, 

 while the end of the stalk which it left shoots 

 forth a new cluster. The current above mentioned 

 is sometimes produced without any revolution of 

 the cluster of globules, at other times I have ob- 

 served the whole cluster to revolve. The magni- 

 fying power which I employed, while making the 

 drawing of this figure, was nearly 500 times. The 

 medium diameter of the clusters, while attached to 

 their branches, I find to be about the 800th part of 

 an inch; and when fully developed and separate, 

 about l-400th of an inch. Miiller discovered these 



animalcules in river-waler in the month of Novem- 

 ber. Those on which the above observations were 

 made, I found in the month of June, in some pond- 

 water." 



Enchelis "This genus of animalcules, according 

 to Miiller, contains twenty-seven species. His de- 

 finition is, 'a simple invisible animalcule, of a cylin- 

 drical form.' " " The size of the different species 

 varies considerably, and therefore requires different 

 magnifying powers to exhibit them (from 200 to 

 500 linear). If the reader have an opportunity ot 

 examining any of them, in instruments of different 

 constructions, but of the same magnifying power, 

 he will readily perceive that there is something be- 

 sides magnifying power that is essentially requisite 

 in a microscope, in order to show the details of 

 objects." 



Fig. 61 The Egg-shaped Enchelis "This 



animalcule is distinguished by its pellucid appear- 

 ance, and the longitudinal folds of the external 

 membrane. A few bright spots are also sometimes 

 observed ; these have been supposed to be the ova, 

 but it is more probable they are the sacs of the poly- 

 gastric structure. The figure is a magnified repre- 

 sentation, showing the sacs and folds, neither of 

 which are constant. Found in stagnant water." 



Vibrio. " The extensive range of this genus, in 

 regard to the structure, form, and size of the differ- 

 ent species, offers great variety to the observer." 

 "It includes animalcules, both membraneous and 

 crustaceous : some as slight as a thread, others whose 

 breadth nearly equals their length ; some whose 

 organization is so complete that modern naturalists 

 have entirely excluded them from the phytozoa; 

 and others, which are with difficulty distinguished 

 from vegetables. To diminish somewhat these in- 

 congruities, without rendering the arrangement 

 complex, I have separated them into three divi- 

 sions. The first is the simplest, and requires a 

 magnifying power of from 200 to 500 times to ex- 

 amine them; the second and third vary so much in 

 size that some do not require half that power, and 

 a few even less, being just descernible by the naked 

 eye. The definition given by Miiller to the ani- 

 malcules under this name, is, an invisible worm, 

 very simple, round, and rather long.'' 



First-division, Bacillaria. " These minute and 

 inactive animalcules are covered with a hard shell- 

 like coat, and appear closely allied to some of the 

 fresh -water Algae, and are not very appropriately 

 classed with the f^'ibrio." 



Second division, Phytozoa. " This term was 

 first made use of by Goldfuss, and is confined by 

 Ehrenberg to those microscopic creatures whose 

 digestive organs are polygastric, or, if they possess 

 a simple alimentary canal, it is always accompanied 

 by rotatory organs." 



Third division, Entozoa. Includes those ani- 

 malcules of the Vibrio genus, which " possess an 

 alimentary canal, but no cilia, nor occasion currents 

 when immersed in a mechanical solution of coloured 

 particles." 



Fig. 68. The Stick Vibrio. 1 ' This animalcule, 

 or rather congeries of animalcules for they are 

 mostly attached together in different forms when 

 magnified appear like pieces of straw of a pale 

 yellow colour, with the inside of an orange brown. 

 They are nearly round, and, if attentively watched, 

 may be seen occasionally to turn upon their longer 

 axis, when a longitudinal line may be observed ; 

 this is probably the hinge or opening of their shell. 

 They vary in length from l-100th to l-500th of 



