120 



THE FORAMIN1FERA 



gerina or Orbulina] almost nothing of a definite character is 

 known. 1 



ORDER Eotalidea. 



Schlumberger has found Rotalina pleurostomata, Schlumb. 

 ( = Pulvinulina partschiana, d'Orb.), to be dimorphic (51), and I 

 have found the same in Rotalia beccarii, Linn. Among seven 

 examples of this species six were megalospheric, and one micro- 

 spheric. In these M = 55 p (limits of variation 37 and 65 /x), and 



FIG. 50. 

 Rotalia bcecarii, L., seen from the superior (a) and inferior (b) surfaces, ap, aperture, x 80. 



m = 1 3 /x. There appears to be no difference in the mode of 

 arrangement of the chambers in the two forms, but the nuclear 

 characters agree with those of Polystomella. I have observed the 

 production of a brood of megalospheric young by a microspheric 

 parent of this species, the process agreeing with that described in 

 Polystomella (20, p. 436). 



Similarly in Calcarina kispida, Brady, M = 49 /x (limits of varia- 

 tion in twelve examples 39 and 59 /x), m= 13 /x (limits 12 and 

 14 /x), and here, again, I found a microspheric specimen with 

 megalospheric young, which in this case were contained within 

 the parent shell. 



The rose-coloured adherent tests of Polytrema are common on 

 coral and other objects from tropical and sub-tropical shores. 

 They may be depressed and encrusting, but frequently rise from 

 an expanded base into arborescent forms. They are built up for 

 the most part of numerous successive laminae of hard perforated 

 shell substance, produced inwards at short intervals into hollow 

 pillars (Fig. 51, a, p\ which are connected with the underlying 

 shell lamina. The openings of the pillars of the superficial layer 



1 The fact that the Orbulina chamber is formed in the later stages of growth of 

 the individual, which in its earlier stages formed the enclosed Globigerina chambers, 

 was first definitely stated by Rhumbler (34). The view had, however, been previously 

 suggested by Major Owen (32, p. 147). 



