124 



THE FORAM1NIFERA 



into fragments. In the specimen, the central chamber of which 

 measures 9 /A in diameter, 6 nuclei are clearly seen. In the 4 

 remaining multinuclear specimens the mean diameters of the 

 central chambers are 22, 18, 12, and 12 /z. 



Now it is possible that all these examples of Discorbina belong 

 to a single series illustrating the phases of the life-history which 

 Schaudinn has followed in aquaria, but the coincidence of the 

 occurrence of the multinuclear condition with the very small 

 central chamber, 9 p in diameter, suggests that Discorbina is, like 

 its allies, a dimorphic form. On this view we may regard the 

 specimens with a single nucleus as megalospheric, and the specimen 



5 33 S 



FlO. 52. 



Table showing the dimensions in micromillimeters of the central chambers of 159 specimens of 

 Discorbina globularis, d'Orb. 



with (at least) 6 nuclei and a central chamber 9 /LC in diameter as 

 microspheric. The remaining multinuclear specimens may consist 

 of megalospheric individuals, the nucleus of which is breaking up 

 prior to reproduction, or of microspheric individuals with a larger 

 microsphere, or, and more probably, of both kinds. 



On this view the form of reproduction which Schaudinn 

 described in Discorbina is the production of megalospheric young 

 by a megalospheric parent which is, as we have seen, of frequent 

 occurrence in other genera. 



The formation of zoospores by the megalospheric parent was 

 not observed among the specimens kept in aquaria, but we are 

 still at liberty to suppose that this phase of the life-history may 

 occur in the natural state. 



Truncatulina lobatula, \V. and J., affords another instance of the 



