THE FORAMINIFERA 



7W.C, 



and 11, c). In the first convolution of chambers the alar prolonga- 

 tions are hardly formed, but as the series is followed on, they 

 project more and more at the sides, overlapping the chambers of 

 the preceding convolutions ; and as they increase the number 

 of apertures between successive chambers, single in the earlier 

 chambers, also increases (Fig. 

 8, A, Fig. 9, st), so that in 

 the terminal chamber there 

 is, as we have seen, a V- 

 shaped row of pores leading 

 to the exterior. 



In the microspheric form 

 the arrangement is similar in 

 the later chambers, but in this 

 form the retral processes are 

 absent from the chambers of 

 the earlier convolutions (Fig. 

 8,J). 



The main trunks of the 

 Canal System lie in the um- 

 bilical region. 1 



They consist of a spiral 

 canal, on either side of the 

 test, running parallel with 

 and just internal to the 

 lateral margins of the cham- 

 bers whether these are pro- 

 duced into alar prominences 

 or not (sp.c, Figs. 9 and 

 11, c). Opposite the inter- 

 vals between the chambers 

 meridional canals (m.c) are 

 given off, and run in the 



passing throug 



other chambers, in order to show the disposition 



ft. 



thickness of 

 some little 



the septa, at 



Fio. 9. 



> Diagram of a section through a megalospheric 

 example of Polystomella crispa. It is represented as 

 jh the megalosphere but between the 



frrtm f the canal system. M, the megalosphere; m.c, 

 1 meridionial ^ . r mpr> re ' tral presses ; j>.c, spiral 



their OUter margins, to meet canals ; st, protoplasm traversing the apertures be- 

 tween the chambers. The dotted portion indicates 



one another in the median 

 plane. From these numbers 



the protoplasm filling the chambers, but the canal 

 system is represented as empty. The numerous 

 minute pores leading direct from the chambers to 



of short Canals Dass Outwards tne exterior are omitted, arid the shell substance is 

 , . . ' r , . ' left blank. 



and, in the case of the outer 



convolution of chambers, open to the exterior, into the pits 



1 The canal system is said by Carpenter to be imperfectly developed in Polystomella 

 crispa (8, p. 282), and Mdbius (25, p. 103) places P. craticulata, Fichte and Moll, in 

 a new genus Helicoza, on the ground, that it possesses a branched canal system, absent 

 in Polystomella. In decalcified specimens of P. crispa, however, whose protoplasm 

 has been coloured dark by osmic acid, it is easy to convince oneself of the existence 

 of the system. 



