16 RHIZOPODA. 



second, so that the several portions of the sarcode 

 body contained in the entire series of chambers 

 are all united by means of connecting bands 

 or ' stolons,' of the same substance {fig. 3, h'). If 

 the successive chambers gi-adually increase in 

 size, a conical shell will be produced. If, again, 

 each of the newly formed chambers, instead of 

 being developed in the axis of its predecessor, be 

 turned slightly to one side of the latter, the whole 

 series will assume a curved figure, and this may be 

 carried to such an extent as to confer on the entire 

 shell a spiral or convolute forrii. If the several 

 convolutions of one of these spiral forms all lie in 

 the same horizontal plane, as in Polystomella or 

 Kumrmdites {fig, 3, c and l/), the shell is said to 

 be ' equilateral.' But if the successive chambers be 

 developed on one side of the plane of the first 

 chamber, so that the spiral passes obliquely round 

 an axis, the shell assumes a more or less pyra- 

 midal form, and is termed * trochoid ' or ' inequi- 

 lateral.' These latter terms may also be applied to 

 such shells as Textularia {fig. 3, /), which appa- 

 rently consist of two or more oblique longitudinal 

 rows of chambers, but in reality differ only from 

 the true spiral forms in the smaller number of 

 chambers which occur in each of the convolutions. 

 A different mode of growth prevails among the 

 MiliolincE. These are usually somewhat oblong in 

 figure, each of the newly formed chambers being 

 equal in length to the entire shell, so that, as 

 growth proceeds, the terminal orifice is alternately 

 transferred from one end of the shell to the other. 

 Hence, in these shells, the addition of successive 

 segments has been compared to the winding of the 

 thread round a ball of worsted {fig. 3, g). 



