10 



POLYGASTRTA. 



segments of the compound body, which enables 

 them to change their situation relative to each 

 other. 



In the next family, Closterium, (6, 7, Jig. 5,) 

 the locomotive organs present themselves under 

 a very different aspect, as, indeed, do the 

 animalcules themselves. The animalcules are 

 incased in a thin, transparent, shuttle-shaped 

 shell, or mantle, (urceolus,) which is in many 

 species evidently open at both ends. Enclosed 

 in this shell is the exceedingly soft and trans- 

 parent mucus-like body of the animal, which 

 is frequently entirely full of green-coloured 

 granules and little vesicles. The shell or 

 mantle, when exposed to heat, is reduced to 

 ashes and entirely volatilized, crisping up 

 during the process like horn. 



The locomotive apparatus is exceedingly sin- 

 gular in its conformation ; it consists of nu- 

 merous very short, delicate, transparent organs, 

 having the form of conical papillae : these are 

 situated in the neighbourhood of the two open- 

 ings in the mantle, lying in the inner space, and 

 can be protruded externally to a short distance. 

 It becomes evident, on mixing a few coloured 

 particles with the fluid in which the animal is 

 contained, that these are instruments of loco- 

 motion. 



The family Astasia (1, Jig. 6) contains nu- 

 merous genera remarkable for the contractile 

 power of their bodies, which causes them con- 

 tinually to change their shape, and consequently 

 they become very puzzling objects to the inexpe- 

 rienced microscopist. Many of them are exceed- 

 ingly beautiful on account of their rich colours ; 

 and so enormously do they abound under certain 

 circumstances, that the water in which they are 

 found is changed to red, green, or yellow, in 

 accordance with the tint of the species which 

 multiplies therein. In many species of this 

 family, contractile proboscides have been found 

 to exist, which most probably form the loco- 

 motive apparatus common to the group. Ani- 

 mals very similar to the Astasians, but lori- 

 cated, constitute the family Dinobryina, (6, 

 Jig. 6,) the envelope forming an urceolus, in 

 which the highly contractile body of the ani- 

 malcule is lodged, having much the appearance 

 of a microscopic Sertularin. 



In the next family, Amoeba, locomotion is 

 accomplished in a most extraordinary manner, 

 these animals apparently possessing the power 

 of making foot-like processes for themselves, 

 or dispensing with them altogether, just as cir- 

 cumstances render it convenient. The Amoeba, 

 or Proteus, as it was formerly named on ac- 

 count of the facility with which it changes its 

 form, seems to have its body composed of a 

 greyish mucus-like jelly, the shape of which is 

 perpetually changing, sometimes shrinking into 

 a rounded mass, then extending itself in all 

 directions as though it was entirely fluid, or 

 shooting out processes of different kinds from 

 any part of the periphery of its body : its 

 movements indeed seem to be rather fluent 

 than progressive, so easily dees it mould itself 

 to any required form. It is, nevertheless, very 

 voracious, and its shape is frequently found to 

 be modified by the contour and dimensions of 



other animalcules which it may have swal- 

 lowed. (7,8,9,10,11,12,13,^.6.) 



Fig. 6. 



1. Astasia Jiavicans. 2. Amblyophys viridis. 3. 

 Euglena a&is. 4. Chlorogonium euchlorum, 5. Co- 

 lacium stentorum on a portion of the leg of a monoculus. 

 6. Dinobryon sertularia. 7, 8, 9, 10, 11, 12, 13. 

 Amoeba diffluens, exhibiting a few of its changes of 

 form. 



The genera Difflugia, Arcella, and Cyphidium 

 (1,2, 3, Jig. 7) seem to be merely Amoebae 

 endowed with a power of constructing for them- 

 selves a carapax or shelly covering of various 

 forms, from the orifices of which the fluent 

 body of the animalcules can be made to protrude, 

 and thus become convertible into instruments 

 of locomotion. 



In Cyclidium, Pantotrichum, and Ch&to- 

 monas, and their loricated representatives, Ch&- 

 totypla, Chtftoglena, Peridinium, and Gleno- 

 dinium, forming the families Cyclididae and 

 Peridinaeadae, we first find a new system of 

 locomotive organs making their appea'rance in 

 the shape of vibratile cilia. 



The locomotive cilia are variously disposed 

 in different genera ; sometimes they are disse- 

 minated over the entire surface of the animal, 

 either irregularly or arranged in regular rows ; 

 sometimes they are only partially distributed 

 or are confined to the region of the mouth and 

 anterior part of the body ; but, whatever their 

 situation, their action is similar; they are inces- 

 santly in a state of active motion, either pro- 

 pelling the animalcule through the water, or 

 causing currents to flow in definite directions, 

 by the agency of which food is brought to the 

 oral opening. 



Fig. 7. 



1. Difflugia ottonga. 2. Arcella dentata. 3. Cy- 

 pkidium aureolum. 



