GUIDE TO THE CORAL GALLERY. 



PROTOZOA OR SIMPLEST ANIMALS. 



Introduction. 



The majority of the Protozoa are extremely small objects, being High Wall 

 in many cases invisible or barely visible to the naked eye. Conse- ^^^^g^ of 

 qnently, excepting in certain instances, diagrams and models are Gallery. 

 exhibited in place of specimens.^ 



The Protozoa are essentially composed of one " cell." The word 

 " cell " was originally used to describe a vegetable cell or vesicle with 

 its walls and fluid contents, just as we speak of a bottle of wine ; 

 but now the term is used for the minute corpuscles of protoplasm 

 or living substance which build up animal and vegetable structures. 



The Protozoa stand in contrast with all the rest of the Animal 

 Kingdom or Metazoa, the latter being composed of many cells of 

 different kinds united into a commonwealth organised on the 

 principle of division of labour. In the figure of Hydra (p. 39), for 

 instance, we see a sac composed of two layers of " cells," those of 

 the inner layer being concerned in the digestion of food, those of 

 the outer having protective and sensory functions ; here each cell is 

 subordinate to the community of cells and cannot live independently. 

 Many Protozoa form colonies, but the individual cells resemble each 

 other, and each cell is independent of the others. 



By way of introduction to the subject, a brief description of a 

 Protozoon is given below. 



Amoeha proteus, or the Proteus Animalcule (Fig. 1), resembles 

 a tiny blob of whitish jelly about ^^ of an inch in diameter ; it is 

 commonly found at the bottom of ponds on the ooze, where it creeps 

 about in search of food. 



The Amceba, observed under the microscope, usually seems 

 globular and motionless at first, but presently beads appear on the 

 surface, some of which enlarge and flow out in the form of finger-like 



' The diagrams and models exhibited in the Case are referred to in the 

 text as "Plate]" and,," Model," with their appropriate number. 



