PROTOZOA. 



GYMNOMYXA AND CORTICATA. 



The Protozoa fall into two fairly well-defined Phyla, in 

 accordance with an important character. In the Gym- 

 nomyxa the body of the animal consists of naked protoplasm 

 which has no definite shape of itself. In many cases the 

 protoplasm has a shell to which it clings, inside or outside 

 of it, and under tonic contraction or when the vital 

 processes are dormant it assumes a spherical shape. The 

 nakedness of the protoplasm implies a very low differentia- 

 tion, the alimentary functions of ingestion and egestion being 

 co-extensive with the surface {cf. Amoeba). In the Corti- 

 cata the living organism assumes a definite shape, which is 

 maintained by a hardened cortex and often a cuticle as 

 well. The form of the body is not determined each 

 moment by the forces acting upon it, but a definite shape or 

 plan is assumed and adhered to for each species. A 

 definite mouth, definite egestive spot and definite motor 

 organs are involved. The Corticata are evidently a great 

 step in advance of the Gymnomyxa, from which apparently 

 they have been derived. 



PHYLUM GYMNOMYXA. 



Fig. 32. — Types of Foraminiferan Shells (After D'Orbigny) 



Nodosaria, 



Glandulina. 



Uvigerina. Bulimina. 



Calcarina. 



PeneropHs. Planorbulina. 



