the recent Alveolina boscii the chambers are further subdivided by 

 horizontal septa. 



Schlumberger states (51) that Munier-Chalmas has recognised 

 the phenomenon of dimorphism in a fossil Alveolina, of which the 

 microspheric form is distinguished by a very small central chamber 

 surrounded by five simple chambers, which are not subdivided. 

 It would appear, therefore, that a peneropline stage is represented 

 also in the development of the microspheric form of this genus. 

 In specimens of the megalospheric form of A. boscii I find the 

 central chamber to be ovoid and to measure about 150 p. in long 

 diameter. 



Life-histories and nuclear characters of the Miliolidea. 



Direct observations on this head are very scanty. 



In Cornuspira, as we have seen (p. 74), the megalospheric 

 form may give rise to megalospheric young, and the same event 

 has occurred in a specimen of a Milioline form (1 Quinqueloculina) in 

 my possession. In this case the megalosphere of the parent was 

 only 30 //, in diameter, and those of the young varied from 20 to 

 43 fji. Schlumberger (49) and Schaudinn (42) have also described 

 the production of broods of young, which were evidently megalo- 

 spheric, in the Miliolinidae (the latter author in Quinqueloculina 

 seminulum, L.), but the nature of the parent is not indicated. In 

 these Miliolinidae it appears that the division of the protoplasm to 

 form the young may occur within the parent test or outside it. 



The production of megalospheric young by the breaking up, 

 within the test, of the protoplasm of a megalospheric parent, had 

 occurred in a specimen of Peneroplis described by Schacko (39) ; 

 and in this case the young, consisting of the central chamber and 

 spiral passage, resemble in size and shape the corresponding parts 

 of the parent. Biitschli (7) has found a single nucleus in two 

 specimens of Peneroplis, and 18-20 in another. In all three cases 

 the parents were megalospheric, and in the last we may suppose 

 that the division of the nucleus had occurred preparatory appar- 

 ently to the production of a brood of megalospheric young, as in 

 the cases of Discorlina and Patellina (see p. 123). 



Of the genus Orbitolites our knowledge is somewhat fuller. 



I have a specimen of the megalospheric form of 0. marginalis 

 in which the two or three peripheral annuli contain young, con- 

 sisting of the megalosphere and spiral passage. The chambers 

 containing them are in this case not different from the ordinary 

 marginal chambers. 



A specimen described by Semper (63) appears to have belonged 

 to 0. duplex, and this also is a megalospheric parent with megalo- 

 spheric young. He mentions that the chambers containing them 



