8UBKINGD0M PROTOZOA. 



19 



the body is occupied by a spherical mass surrounded by a 

 firm chitinous covering and forming the central capsule. This 

 contains usually many nuclei as well as vacuoles, oil-globules, 

 and in some cases crystals and pigment-granules. The wall 

 of the capsule is probably comparable to the shell of the 

 Foraminifera, being perforated as in those forms by minute 

 pores through which the intracapsular protoplasm becomes 



\^ 





Fig. 7. — ThalasucoUa pelagica (after Haeokel from Hatschek). 



continuous with the extracapsular. This latter portion on 

 this supposition, notwithstanding its greater relative thick- 

 ness, is equivalent to that portion of the protoplasm of the 

 Foraminifera which is outside the shell and from which the 

 pseudopodia arise. It is usually richly vacuolated and pig- 

 mented, but contains no nuclei ; the axial supports of the 

 pseudopodia traverse it and take their origin from the inner 

 layers which immediately surround the central capsule and 

 are more homogeneous than the outer portions. 



The shell is very various in form in the different genera, 

 reaching a high degree of differentiation in some forms, such 

 as Heliosphcera (Fig. 8), where it consists of a fenestrated 

 globe traversed by radiating spines. Its greatest simplicity 

 is seen in Sphcerozoum, in which it is represented by scattered 



