266 p. JEFFREY BELL. 



single cells were very small, only 2*5 microm.,^ at times, in 

 diameter, of circular, oval, or — owing to pressure — angular 

 shape. The shades of colour, exhibited by their contents, 

 always gave the Bacterio-purpurin absorption bands (Lan- 

 kester), and exhibited the same chemical characters as that 

 colouring matter, which is quite diiFerent to that of Monas 

 (Micrococcus) prodigiosa. The cell-membrane, which resem- 

 bles that of GlcBocapsa, is generally very distinct, on account 

 of this coloration ; within are to be found very remarkable, 

 dark granules ; on account of their intercellular substance, 

 which ordinarily separates the cells from one another by 

 about their own diameter, Cohn would place this alga among 

 the Chroococcaceee ; in addition to this, there is a general 

 membrane for the cell-family, which is, however, observed 

 with difficulty, unless some such pigment as carmine or 

 gamboge be added to the water. The observation of their 

 development is not altogether easy ; at first the cell-families 

 have not a circular but a vesicular or sack-like form ; often, 

 by the excessive development of cells in a certain direction, 

 the whole takes on a bell-shaped form ; these gradually 

 become spherical, and further increase by the appearance of 

 tertiary protuberances. If this Clathrocystis suffers from a 

 want of water, daughter- cells are not formed, and the cell- 

 families come to resemble Hydrodictyon by the appearance 

 of large spaces in their midst; breaking up into smaller 

 portions, they sink to the bottom of the vessel, and find a 

 resting-place, on the decaying animal and vegetable matter 

 which may happen to be there ; from these, in time, spring 

 up well-formed circular, and even net-like families of cells 

 (fig. 10). 



A remarkable mode of reproduction still remains : Cohn 

 discovered young cell-families containing a definite (16 — 64) 

 number of cells, united into a regular sphere, in such a way 

 that they were closely pressed to one another, and seemed to fill 

 the sphere ; they differed from the rosy-peach-coloured families 

 by an intensely purple-red coloration ; but still more, by ex- 

 hibiting spontaneous movement, turning round and round 

 like Volvox or Pandorina ; of its cause and of the length of 

 its duration nothing can be said, but no such movement has 

 ever yet been observed in any of the allied Chroococcacea. 



7. Monas vinosa (fig. 13), Ehr. Next in order our author 

 deals with the actively mobile, red corpuscles, which go under 

 this name, and which he found in the same vessel with the 

 peach-coloured Clathrocystis ; of regularly spherical or oval 

 form, often found in couples, their greatest diameter was 2"5 

 ' 25 Micromillimeters = 0.0025 ram. 



