356 



NATURAL HISTORY. 



This is a common instance of the order of the class Infusoria, called, from the body being more 

 or less covered with cilia, the INFUSORIA CILIATA. 



The highest powers of the microscope, and glasses possessing very perfect defining qualities, are 

 requisite in order that the next type of Infusoria may be seen perfectly. The little creatures are free 

 swimming, and the body is long, egg-shaped more or less, but it has a projection so as to render it more 

 or less spindle-shaped or fusiform. In front, there is a single filament prolonged from the body like a 

 very large cilium, and a longer one, about twice the length of the body, projects behind. These are 

 the flagella. There is a single minute contractile vessel in the body on one side, and the nucleus or 

 endoplast is spherical, and near the centre of the animal. There is no mouth or special aperture for 

 food, and there are no cilia on the soft external part, which barely differs from the inner mass of the 

 minute body or endoplasm. Only measuring from o-^nnyth to ^th of an inch in length, these minute 

 Infusoria are found in vegetable infusions. They swim freely by means of their long flagella, and 

 also crawl over substances very much after the fashion of Amrebse. It may happen that one may be 

 seen larger or broader than the others, and, after a while, the observer is repaid by seeing the body 



Fig. 4. GENERA OF CILIO-FLAGELLATE INFUSORIA. 



A, Mulodiniuni iibcrriraiim : B, Glenodinium acumiuatum : c, Diplopsalis lenticnla: D, Gymnodiniura spir.ile: E, Ceratium tripos; F. Peridiiiuim 

 tabiilitura ; G, Ct'ratium loiigicorne; H, 0. fusus, I, Stephanomonas locellus ; J, Mitopuora dubia; K, Heteromastix i>roteiformis, 

 L, Mallomonaa plosslli. 



split down its length, and two creatures swim off, each supplied with a front and rear flagellum. If 

 two come in contact, they join together, like Amoeba, and after a while the mass loses its flagella, and 

 a vast number of spores are formed out of the endoplasm. These escape, and gradually form into 

 creatures like those which produced them. 



Exceedingly minute particles of food are taken in by the surface of the body at no particular spot, 

 and the undigested matters simply pass through the endoplasm to the outside. This Infusorian is a 

 Cercomonas* (Fig. 3), and is a fair example of the order called the FLAGELLATA. Members of this 

 order are distinguishable in some instances with difficulty from moving spores of the lower plants, 

 and indeed it is in this group that the junction of the animal and vegetable kingdoms is to be 

 found. The Flagellata contain very simply-constituted organisms, and some which are less so, and of 

 these last the phosphorescent marine Noctiluca is an example. 



Another type of Infusoria combines, as it were, the characters of the ciliated animalcules and 

 those which have a flagellum. The kinds which are associated with it are mostly found in sea water, 

 and in many parts of the globe. A few, however, are to be noticed in fresh water in the United King- 

 dom. Thus, Professor Allman found enormous multitudes of an Infusorian about -g-^th to YoW^h of 

 an inch long, of a reddish-brown colour, in the ponds in Phoenix Park, Dublin. It had an almost 

 globular body, with a constriction or furrow running round the middle, and a groove passing from this 

 furrow over the body to the top. The whole surface was covered with extremely delicate moving cilia, 

 and a long, slender, active cilium or flagellum was found to be placed on the top in the groove. A large 

 endoplast (nucleus) was in the centre of the animal, and just below the origin of the flagellum was a 

 small, intensely red spot. A contractile vesicle occurs in this type. The brown colour of the ponds in 



* Cercomonas typica. 



