166 J. J. LISTER. 



3. The two forms differ in the frequency of their occurrence, 

 the megalospheric form being much more abundant than the 

 microspheric. 



In Polystomella crispa (Linn.), among the examples that I 

 have seen, the proportion of the megalospheric forms to micro- 

 spheric is as 34 to 1*. In Adelosina polygonia, ScHLUM- 

 BERGER gives the relative proportions of the two forms as 8 

 to 1. 



4. The megalospheric form arises as a young individual 

 already invested by a shell, which may be found lying in or 

 about the peripheral chambers of the parent. Such megalo- 

 spheric young have been seen in — 



MilioUnce, by Gervais (12), M. Schultze (38), Schlum- 

 BERGER (32), and Schneider (37). 



Peneroplis proteiis, d'Orb., by Schacko (29). 



Orbitolites, simple form, by Semper (43). 

 „ complanata, Lamk., by Lister. 



„ complanata, var. laciniata, Brady, by Parker, 



Carpenter, Brady (2), and Lister. 



Spirillina vivipara, Ehrb., by Ehrenberg (11), and Stret- 

 HiLL Wright (45). 



Cristellaria crepidula (Fichtel and Moll), by Brady (1). 



Rotalina, sp., by M. Schultze (40). 



Calcarina hispida, Brady, by Lister. 



Megalospheric young may be produced both by microspheric 

 and megalospheric parents. 



In the specimens of Orbitolites complanata, var. laciniata, 

 described by Brady, and in those which I have examined, the 

 parents of such young are microspheric. 



In Max Schultze's account of the production of young by 

 one of the Miliolidse, it is stated that the parent was dis- 

 tinguished from other individuals in the aquarium by its large 

 size. As it is generally the case in this family that the micro- 

 spheric form attains a larger size than the megalospheric, it is 

 probable that in this case also the parent was microspheric. 



* Among specimens collected in July and August, 1894, the microspheric 

 forms were, however, more abundant than here indicated. 



