74 THE FORAMINIFERA 



which is found at the centre of the megalospheric form (Figs. 37, 

 A, and 38). 



This process is clearly comparable with the formation of the 

 megalospheric young by a microspheric parent which we have 

 followed in Polystomella, the chief difference consisting in the fact 

 that the young are formed in peripheral brood chambers and not 

 outside the test of the parent. 



By analogy with Polystomella we cannot doubt that megalo- 

 spheric parents give rise to zoospores. Specimens of Orbitolites 

 have, however, been found (and the corresponding phenomenon 

 has also been observed in several other genera) in which a 

 brood of megalospheric young occupies the peripheral chambers 

 of a test, the centre of which is formed by a primitive disc, and 

 which is therefore megalospheric (20, p. 435). Hence we must 

 conclude that in these cases the megalospheric form may be 

 repeated, possibly more than once, before a brood of zoospores 



is produced. The behaviour of the 

 nucleus under these conditions has 

 ^ not been closely followed. 



& gj _ Fig. 13 illustrates a similar repe- 



tition of the megalospheric form in 

 the case of Cornuspira involvens. 1 



The Relation between the Microspheric 

 and Megalospheric Forms. 



With the evidence furnished by 

 the life -histories of Polystomella and 

 ^^f nsp ^ ra inv ^ wn t' . Reuss - , The Orbitolites we may now return to the 



contents of a megalospheric form have J 



emerged from the shell and divided up question of the relationship of the 



into a number of young, which are also TV.- j i_ r 



megalospheric. in bSth parent and megalospheric and microspheric forms. 



young the megalosphere was about TViP Parlipor VI'PW liplrl nn this 



80 n in diameter, x 30. Cp. Fig. 20. earliest V16W J 



subject, that they represented two 



species of a genus, is at once disposed of by the fact that the 

 megalospheric form is the offspring of the microspheric. 



The next suggestion was that the two forms represent the two 

 sexes. 



To this, two objections may be made on general grounds. 

 (1) The difference between them is most marked at the beginning 

 of their growth, when they consist only of the central chambers, 

 the microsphere or the megalosphere, while males and females 



1 In his preliminary paper Schaudinn states (44, p. 96) that the megalospheric 

 generation may also be repeated (though rarely) in Polystomella, and that in such an 

 event- no principal nucleus is formed by the megalospheric parent. As Rhumbler 

 remarks in his notice of Schaudinn's paper (Zool. Centralblatt. Jahrg. 2 (1895), 

 p. 453, footnote), it is difficult to see how this result can be reached, for the shell of 

 Polystmnella is too thick to allow the nuclear condition to be observed during life. 



