IMPOETANCE TO ZOOLOGIST AND GEOLOGIST 9 



stratified Avith other deposits in almost every 

 geological formation. 



It is therefore essential that the stratigraphical 

 geologist, in studying the sedimentary rocks, should 

 become acquainted with the principal types of 

 Foraminifera likely to be met with in this way. 



The Stkucture and Classification of the Peotozoa. 



The Protozoa, of wdiich the Foraminifera con- 

 stitute an important group, are characterised by their 

 simplicity of structure as compared with the higher 

 animal groups, the metazoa. In this respect they 

 correspond with the similarly elementary forms of 

 vegetable life sometimes called the protophyta ; and 

 indeed it is difficult, if not impossible in some cases, 

 to assign them to either the animals or the plants. 



The protozoa are typically unicellular — that is to 

 say, they often consist of a single animal cell which, 

 with its nucleus, is complete in itself for the functions 

 of life and growth. Any increase which takes place 

 is made on the same general plan as the previous 

 cell— that is, without any special differentiation of 

 its structure, such as the formation of tissue, for any 

 particular function. The protozoa consist of a 

 jelly-like substance having a colloidal consistency, 

 called sarcode. The sarcode has the ability to throw 

 out extensions from the main mass, either of blunt 

 processes or of fine hairlike extensions. The sarcode 

 body may be naked or having a covering which 

 in some cases is of extreme tenuity ; in others 



