PROTOZOA; FORAMINIFERA. 57 



purely arbitrary. Of the two, Schultze's arrangement is pro- 

 bably the more satisfactory. 



Table of D'Orbigny's Arrangement of the Foraminifera. 



Order I. MonosUga. — Body consisting of a single segment ; the shell of 

 a single chamber. 



Order 2. Stkhostega. — Segments arranged in a single row, in a straight 

 or slightly curved line. 



Order 3. Helicostega. — Segments arranged in a spiral, the shell forming a 

 number of convolutions. (The ' ' nautiloid " Foraminifera. ) 



Order /^ Entomostega. — Segments arranged on two alternating axes, 

 forming a spiral. 



Order 5. F.nallostega. — Segments arranged on two or three alternating 

 axes, not forming a spiral. 



Order (>. AgaMstega. — Chambers wound round an axis, each segment 

 embracing half the entire circumference. 



Table of Schultze's Arrangement of the Foraminifera. 



Stction I. Helicoidea. — Segments arranged in a convolute series. 

 Section 2. 'Rhabdoidea. — Segments placed in a direct line. 

 Section 3. Soroidea. — Segments disposed in an irregular manner. 



Affinities of Foraminifera. — ^The Foraminifera are re- 

 lated on the one hand to the Amoebea, and on the other to the 

 Spongida. From the former the " unilocular " Foraminifera 

 differ, both in the possession of an external envelope, and in 

 the much less highly differentiated characters of their sarcode ; 

 but the points of resemblance are obvious, and in such forms 

 as Actinophrys and LieberkUhnia we are presented with an ap- 

 parent transition between the two orders. From the shelled 

 Amcsbea, such as Arcella, the Foraminifera are broadly separ- 

 ated by the absence in the former of pseudopodial pores, and 

 are fundamentally distinguished by the different nature of the 

 sarcode-body. 



To the Sponges the Foraminifera are related in various 

 ways, one of the most striking links being found in Carpenteria, 

 a singular attached form of Foraminifer. The shell, namely, 

 of Carpenteria is conical and calcareous, composed of an aggre- 

 gation of chambers arranged in a spiral, and having its walls 

 perforated by numerous foramina of minute size. The interior 

 of the chambers, however, is filled with " a fleshy, sponge-like 

 body," strengthened by numerous spicula. Another curious 

 link between the Foraminifera and the Sponges is the Squa- 

 mulina scopula of Carter, which is truly a Foraminifer, though 

 originally referred to the latter. It consists of an arenaceous 

 test, forming a pedestal surmounted by an obversely conical 

 column. Both pedestal and column are more or less perfectly 

 chambered, and are filled with semi-transp'arent yellowish sar- 



