Elphidium is a marine form. It is found creeping on Sea weeds to a depth of 300fathoms

Phylum : Protozoa

Class : Rhizopoda

Order :Foraminifera.

Structure :

Elphidium is also called 'Polystomella is a 'dimorphic rhizopod'. It is a unicellular microscopic protozoan, and" 1 mm in diameter It is pale yellow in colour. It lives in marine water. The body is covered by a shell. The shell is biconvex. The first formed chamber is proloculum. The shell contains spirally arranged V shaped chambers. Hence it is called "polythalamus or multilocular They overlap one another. These chambers show 'openings' hence it is perforate Through these openings cytoplasm will come out. The cytoplasm is produced into a number reticulopodia. which will form a network. From hinder end of each chamber cytoplasmic processes will develop. They are directed backwards. They are called retral processes'.

The chambers are filled with the cytoplasm.

1. The cytoplasm contains one or many nuclei.

2. Contractile vacuole is absent.

3. Mouth is absent.

4. Cytoplasm contains food vacuoles. They take up the process of digestion.

Dimorphism: Polystomella exhibits dimorphism. The individual occurs in two distinct forms.

1. Megalosperic form.

2. Microspheric form.

1. Megalospheric form:

Its proloculum is big in size. A single large nucleus is present in one of the chambers. It takes up sexual reproduction.

2. Microspheric form: Its proloculum is small in size. Many nuclei are present in the cytoplasm. This form reproduces by asexual reproduction.

Locomotion and Nutrition:

Polystomella show slow creeping movements with the help of reticulopodia. It is a holozoic feeder. These Pseudopodia will capture the prey. When it comes in contact with the prey, it kills the prey by secreting toxic substance. The prey is digested in the food vacuole the digested food is absorbed by the cytoplasm.