8 A Guide to the Zoological Collections in the 



Most of the Protozoa are aquatic : the species of one 

 group — the Gregarinida — live as parasites in the interior 

 of the cockroach, the earth-worm, and other animals. 



In the Museum collection the shell-secreting Protozoa 

 are well represented — both actual shells and enlarged 

 models. 



There are two great groups of shell-secreting Protozoa 

 — (i) the Radiolaria, the shells of which consist of flint, 

 and (2) iViQ, Foraminifera,i\\& shells of which consist either 

 of agglutinated sand-grains or, more commonly, of chitin 

 (a flexible horny substance like that which forms the wing- 

 cases of beetles and the integument of Crustacea and many 

 other invertebrate animals), impregnated and strengthened 

 with either carbonate of lime or flint. 



Only the Foraminiferal Protozoa will be here described, 

 as they alone are represented in the collection by actual 

 specimens visible to the naked eye. 



The Foraminifera are aquatic (mostly marine) Pro- 

 tozoa in which the body is enclosed in a shell which is 

 usually perforated all over with little holes like a sieve, 

 whence the name Foramirtifera, but in some cases is 

 entire with at one end a single opening, or mouth, just 

 like, for example, a snail-shell. From the little holes in the 

 shell-wall, or from the mouth of the shell, the living 

 animal puts forth and draws in again thread-like processes 

 of its own body-substance, which are known as pseudopodia, 

 and it is by the continuous motion of these threads of pro- 

 toplasm, or pseudopodia, that the animals move from place 

 to place and seize their minute prey. 



The great majority of the Foraminifera live in the sea. 

 At the surface of the great oceans they exist in countless 

 numbers, and as they die their shells fall to the bottom, 

 where they form deposits of vast extent known as " Fora- 

 miniferal ooze," or, form the name of the commonest and 

 one of the largest of the oceanic species, " Globigerina 

 ooze." When dry this ooze has all the appearance of com- 

 mon chalk, and the White Chalk of Geology is in fact 



