22 



PEOTOZOA—EHIZOPODA 



PHYLUM I 



Fig. 4. 



BiluculinahraO n'l Schlumb. Recent ; Bay of Biscay. 

 A, Small form with megasphere. B, Large form with 

 microsphere. 15/^ (after Schlumberger). 



in having a single nucleus 



When the animal attains its adult stage there is a great increase in the 

 number of pseudopodia, and the entire protoplasm either leaves the test and 



accumulates about the exterior or is 

 drawn into the outer chambers. 

 Finally, each nucleus gathers a mass 

 of protoplasm about itself and secretes 

 the proloculum of a new test. This 

 newly formed proloculum is of the 

 larger type and is the first chamber 

 of the megalospheric form, instead of 

 being of the same size as that of the 

 microspheric parent from which it was 

 derived. The megalospheric form (Fig. 

 4, A) differs from the microspheric form 

 This does not divide, but moves along as new 

 chambers are added, 

 keeping in about the 

 middle chamber nu- 

 merically. Nucleoli 

 appear in increasing 

 numbers as the growth 

 continues, and finally 

 the whole nucleus 

 breaks down and a great 

 number of minute nuclei 

 appear. These draw 

 about themselves por- 

 tions of the protoplas- 

 mic mass and then di- 

 vide by mitotic division. 

 Finall}^, the mass leaves 

 the test in the form of 

 zoospores. These are 

 then supposed to con- 

 jugate and to give rise 

 to the small proloculum 

 of the microspheric 

 form, thus completing 

 the life cycle, although 

 the actual process of 

 conjugation has not de- 

 finitely been observed in 

 this group. The empty 

 tests left behind must 

 form a large propor- 

 tion of the dredged 

 Foraminifera. The 

 two forms may be dis- 

 tinguished by the size 

 of the proloculum and, when sufficiently known, by other characters as well. 



Pig. 5. 



Deep-sea ooze iiiagiiilied 700 diameters, u, Bnthyhiiis witli Coccolith.s ; 

 h, Individual Discoliths and Cyatholiths ; c, Coccos])heres ; d, Olohkierina ; 

 (', Ghthiiiertnn witli luirsted test; /, Textnlnr'ui; ij, (/, Radiolariu ; li, i, 

 Diatoms; 1:, 1, Sponge spicules ; in, Mineral fragment. 



