112 THE FORAMIN1FERA 



were "ziemlich viel grosser" than those internal to them, and 

 thus it may be the case that in this as in other characters 0. duplex 

 is intermediate between marginalis and complanata. 



In 0. complanata the microspheric forms known as var. laciniata 

 produce megalospheric young. The double convoluted margins 

 of this variety are not completely subdivided into chamberlets as 

 are the more central regions of the disc, but, in part at least, con- 

 tain spacious chambers extending through the thickness of the 

 disc, and round a large part of the periphery. Into these (as well 

 as into similar large chambers in the secondary growths formed on 

 the surface of the disc) the protoplasm withdraws, at the reproduc- 

 tive phase, from the whole central region of the original test, and 

 becomes divided up into young megalospheric forms, which are 

 liberated by the breaking down of the limiting walls. This mode 

 of reproduction in 0. complanata was first described by Brady (4), 

 though he was not aware of the full significance of his observation, 

 and afterwards by myself (20). In Fig. 36, b, a form with a simple 

 margin is seen bearing megalospheric young. 



The megalospheric form of 0. complanata may also, as we have 

 seen (p. 74), give rise to a brood of young of the same nature, 

 but there can be no doubt that a phase recurs in the cycle of the 

 life-history in which, as in Polystomella, zoospores are produced. 



The microspheric form of 0. complanata has, scattered through 

 its protoplasm, large numbers of rounded nuclei, which may fre- 

 quently be found constricted as though in process of simple 

 division. In the megalospheric form a large nucleus may often be 

 found throughout the greater part of the life lying in the primitive 

 disc, and thus, as already pointed out (p. 71), at the central part 

 of the protoplasm (20). 



Calcituba polymorpha appears to be a degenerate member of the 

 Miliolid stock. Its life-history, as exhibited in aquaria, has been 

 investigated by Schaudinn (46). It forms wide adherent expan- 

 sions on the surface of foliaceous algae on which it feeds, spreading 

 in irregular annular patches like fairy rings. The colony may 

 begin as a spherical central chamber with a spiral passage leading 

 from it the form which occurs so frequently at the centre of the 

 megalospheric tests of the compact Miliolidea. From such a centre 

 branching offsets extend in a radial direction over the algal sub- 

 stratum, and as this is disintegrated by the organism feeding on 

 it, the central regions, left unsupported, may fall away, while the 

 margins spread in the annular fashion described. The portions 

 which so fall may start a similar colony forthwith, or their proto- 

 plasm may break up into small portions (1-20) of varying size, 

 which at first crawl about as naked masses, and later, on initiating 

 a new colony, may secrete the Miliolid form of test mentioned 

 above. 



