THE FORAMINIFERA 



m.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. 

 8,6). 



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 ^-/^ "'': '^''"''./f^T^' r.fli'. 



, A . / ,1 i "* VV3K 1 . .:-. -,'. .// Ay I 



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 

 thickness of the septa, at 

 some little distance from 



Fio. 0. 



Diagram of a section through a megalospheric 

 example of Polystomella crispa. It is represented as 

 passing through the megalosphere but between the 

 other chambers, in order to show the disposition 

 of the canal system. M, the megalosphere ; m.c, 

 meridionial canal ; r.pr, retral processes ; ip.c, spiral 

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

 , . i j. tween the chambers. The dotted portion indicates 



One another in the median the protoplasm filling the chambers, but the canal 

 nlanp "Prnm thpsp nnmhprc; s >' stem is represented as empty. The numerous 

 pldlie. rrom tnese numoers m i nute pores leading direct from the chambers to 

 Of short Canals pass OUtwards, the exterior are omitted, and the shell substance is 



' 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 Mobius (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. 



