332 



BIOLOGY OF THE PROTOZOA 



homogeneous or are perforated hy minute j^ores (foramina) through 

 whieh single pseudojjodia are protruded. The cavity of the shells 

 may be a single chamber, septa if present being incomplete (Mono- 

 thalamous). Or a multitude of chambers may be present separated 

 by partitions or septa (polythalamous). The latter may be compli- 

 cated by secondary deposits of lime through which labyrinthine 

 canals and passages give occasion for intricate designs (Fig. 148). 

 The surfaces of the shells are usually smooth but in some forms par- 

 ticularly the floating t^npes of Globigerina, spines, ridges, rays, etc., 

 j^robably assist in floating. 



The living substance is usuall.y so fluid that it is rarely quiet and 

 ])r<)t()plasmic streaming is so characteristic that the Foraminifera 



Fig. 148. — Polythalamous shell of Operculina (schematic). The shell is repre- 

 sented as cut in different planes to show the distribution of the canals and the arrange- 

 ment of septa and chambers. (After Carpenter.) 



have been favorite materials for the study of proto])lasm. It is not 

 di\ided into zones, and the marine forms have no vacuoles. There 

 are numerous foreign bodies as a rule and aggregates of the residue 

 associated with food substances, form masses of fecal material 

 termed "stercome." In man\ 



small 



sj)orulation of the host organism {('hriisi 



forms living commensals are also 

 vellowish ( Vy])tomonas-like forms 



present in the form of 

 which are liberated with 

 dellu). 



The living protoplasm fills more or less completely all chambers 

 of the organism. In polythalamous forms proto])lasmic strands 

 passing through pores in the septa maintain all i)arts of the soft 

 body as a unit mass. In monothalamous and from the last-formed 

 chamber of polythalamous forms, a large mass of protoplasm gives 



