414 THE CANADIAN NATURALIST. [DeC- 



acting from within, and probably of the nature of muscular 

 contraction. Nor are there wanting indications that these 

 motions are Toluntary and prompted by the appetites and sensa- 

 tions of the animal. Fig. 24 represents one of the states of a 

 specimen from a pond on the Montreal Mountain. 



Another generic form found in the same situation is Actinophri/s, 

 the Sun-animalcule. In this the outer coat is more distinctly 

 marked, and the body retains a globular form, while the pseudo- 

 podia are very slender and thread-like. Fig. 25 represents a 

 specimen found with the preceding. 



Amoeba and Actinophrys belong to a family of Khizopods, 

 (the Amoebina,) which either have no hard covering or a thin 

 crust or lorica covering part or the whole of the body. The 

 remainder of the Rhizopods are protected by calcareous shells, 

 often of several chambers and perforated by pores for the emission 

 of pseudopodia, (Foraviinifera,') or they are covered by a silicious 

 shell or framework of one piece, (^Poli/cystina). The whole of 

 the Rhizopods may thus be included in the following groups, 

 which may be regarded as sub-orders or families : 



1 . Amoehina, without hard skeletons, and mostly fresh-water. 



2. Foraminifera, with calcareous skeletons; marine. 



3. Poli/cysfina, with siliceous skeletons ; marine.* 



The Foraminifera are the most important of these groups, 

 since they occur in immense abundance in the waters of the 

 ocean, and in its deeper parts their calcareous shells accumulate 

 in extensive beds. According to Messrs. Parker and Jones, 

 from 80 to 90 per cent, of the matter taken up by the sounding 

 lead in deeper parts of the Atlantic, is composed of their 

 remains. In like manner, in the sea bottoms of former geolo- 

 gical periods, were accumulated, by the growth and death of 

 Foraminifera, the great beds of chalk and of Nummulitic and 

 Miliolite limestone. In the older formations, also, these creatures 

 are found to have attained gigantic dimensions as compared with 

 living species. A Foraminiferous organism of dimensions un- 

 equalled in the modern seas (Eozoon Canadense, Fig. 36) occurs 

 in the Lower Laurentian, and is the oldest form of animal life 

 known to us. The forms figured (Figs. 26 to 35), as seen under 

 the microscope, are some of the most numerous in the Gulf of 



* Some naturalists form for these a separate class or order 

 {Badioloria). 



