ON THE LIFE-HISTORY OF THE FORAMINIFERA. 171 



sexual nature of the zoospores of the megalospheric form is at 

 present insecure. There is no direct evidence of the conjuga- 

 tion of zoospores or the mode of origin of the microspheric form 

 in a dimorphic species.] 



Postscript 1. 



In reviewing the previous work on the life-history and nuclei 

 of the Foraminifera, I have confined myself to a rather limited 

 range of forms. I have done so because it appeared best to 

 select the evidence of such forms as are most obviously related 

 to those which I had to describe. 



ScHAUDiNN has recently published (31) a preliminary account 

 of his researches into the reproduction and mode of increase of 

 the nuclei in the Foraminifera. This I did not see until after 

 my paper was written. Many of the observations appear to be 

 of the highest interest, but no mention is made of the im- 

 portant fact of the existence of dimorphism. Polystomella 

 vrispa (LiNN.) is described as ixsually having one or four nuclei, 

 but is said to become many-nucleated during reproduction ; a 

 form of reproduction is also described in which the whole of the 

 protoplasm leaves the shell and divides up into numbers of 

 young individuals which assume the characteristic shape of the 

 species. Schaudinn has, however, apparently failed to recognise 

 what is undoubtedly the fact, that in this species one in every 

 thirty to forty individuals is microspheric and possesses nuclei 

 of a quite different character from that of the megalospheric 

 form. 



In his account of the changes which the nuclei of the Fora- 

 minifera undergo preparatory to reproduction, Schaudinn 

 describes a breaking up of the nucleus into fragments which 

 are dispersed through the protoplasm ; in this general result, 

 my observations on the nucleus of the megalospheric form of 

 Polystoviella, so far as they go, agree with his, but I am quite 

 unable to recognise the remarkable phases of the process which 

 he describes in those that I have seen. 



