172 j. j. lister. 



Postscript 2. August 3, 1894. 



It is stated above tliat I had no evidence as to the fate of 

 the microspheric form of Polystomella crispa (LiNN.). 



I have since made further observations on living Fora- 

 minifera (chiefly Polystomella), and have seen in some hundreds 

 of cases the mode of reproduction mentioned by ScHAUDlNN. 



The specimen of Polystomella, as seen attached to the glass 

 walls of a vessel, becomes surrounded by a halo of closely-set 

 radiating pseudopodia. After some hours the protoplasm is 

 withdrawn from the shell, emerging into the area covered by 

 the halo. Here, after involved streaming movements, it gradually 

 divides into distinct spherical masses, which, in the case of 

 the specimens in my jars, usually had a diameter of 50 to 

 60 fi. 



In a short time these masses secrete a shell, and, some 

 four or five hours after they first became distinct, they throw 

 out long pseudopodia, and rapidly draw apart from one another 

 and from the empty parent shell. In the course of a few hours 

 the wall of a second chamber is formed, a third and fourth being 

 added by the second day after separation occurred. In this 

 stage they are readily recognized as young megalospheric in- 

 dividuals. 



After the protoplasm has left the central part of the shell 

 there is no direct evidence, in decalcified specimens, as to 

 the nature of the parent ; but in specimens (some fifty or 

 more) killed and decalcified at earlier stages of the repro- 

 ductive process it is seen that the parent is in every case micro- 

 splicric. 



The fate of the microspheric form of Polystomella crispa 

 (Linn.) is, then, to give rise to megalospheric young. 



In two examples of Rotalia Beccarii (Linn.) the same pro- 

 cess occurred. The parent in each case was microspheric. 



The fact that the whole of the protoplasm of the parent is 

 used in the production of the young, and that these are all of 

 one form, supports the view that the two forms of the Fora- 

 minifera belong to different generations. 



