156 Mr. J. J. Lister. Contributions to [June 7, 



After maintaining their rounded form for a certain time, the nuclei 

 .give off portions of their substance into the surrounding protoplasm. 

 This process appears to begin in the innermost chambers, but it ex- 

 tends to the nuclei in the outermost chambers, and ultimately the 

 whole of the nuclear material is distributed through the protoplasm 

 in the form, in preserved specimens, of irregularly branched and 

 deeply staining strands. Of the further history of the microspheric 

 form I have no clear evidence. 



The Megalospheric form during the vegetative period of its life has 

 a single large nucleus, which grows in size with the growth of the 

 protoplasm, and passes on from chamber to chamber, moving to- 

 wards the centre of the protoplasm contained in the series of 

 chambers, though lagging some distance short of it. It consists of 

 a nuclear reticulum, nucleoli which occupy the nodes of the reticu- 

 lum, and of a substance occupying the meshes. The nucleoli appear 

 to increase in number and diminish in size with the advance of the 

 organism. There is reason to believe that as the nucleus moves on 

 through the chambers portions of its substance are given off into the 

 protoplasm. It appears that this may occur either by the separation 

 of considerable portions, sometimes containing several nucleoli, which 

 lie strewn along the track of the nucleus, or by the dispersal of 

 minute fragments into the surrounding protoplasm, causing in 

 stained specimens a flush in the neighbourhood of the nucleus. In 

 some specimens the nucleus has lost its rounded form, and sends 

 irr.egular processes into the protoplasm. Its staining pi'operties are 

 at the same time diminished. It appears probable that these nuclei 

 are such as have given off a large part of their substances as above 

 described, and are now in process of dissolution. 



In the reproductive phase no large nucleus is present, but hosts of 

 minute nuclei (1 2/t in diameter) are found scattered through the 

 protoplasm. At the same time broad channels of communication 

 have become opened up, setting the inner chambers in direct com- 

 munication with the outer. 



At first the small nuclei are most abundant in the terminal cham- 

 bers, but ultimately they become uniformly distributed through the 

 protoplasm. They then divide by karyokinesis, the protoplasm being 

 aggregated about them in spherical masses, 3'5/t in diameter, each of 

 which contains a dividing nucleus. 



At a later stage each nucleus, presumably the daughter-nuclei of 

 this division, becomes the centre of a flagellated spore. These spores 

 re all of approximately equal size, in other words, they are isospores. 



In one instance spores of a different character were observed 

 escaping. These were anisospores. They consisted of macrospores, 

 globular bodies having a diameter of 11 10/t, and with indica- 

 tions of a flagellum, and microstores of a globular or oval shape, from 



