36 Observations on Cosmarium Margaritiferum. 
tiferum and others of the same family were very numerous. 
During the summer and autumn, the masses of green matter 
would float to the surface, rapidly disengaging oxygen as the 
sun shone upon them, and sinking again to the bottom with 
the coolness of the evening. Later in the year, masses would 
adhere to the inner surface of the bottle in the form of a thin 
pellicle, or collect in slimy masses, which appeared to dis- 
solve with the warmth of the coming spring. The green 
colour changed to that of a reddish-yellow, and it might have 
been thought that all was dead, did not the microscope show 
the same beautiful green both in young and full-grown plants, 
together with much bright red and brown, apparently the 
casings of the sporangia, which gave their colour to the 
wheel-animalcules that had evidently feasted on their remains, 
and thriven on them. Large Cosmaria, still in active motion 
(the remains of the mature growth of the preceding summer), 
lay imbedded in the mass, when a small portion was sepa- 
rated for microscopic observation, as well as clusters of young 
ones, figured at figs. 31, 32, 33. When the bottles had re- 
mained more than a year untouched, except for change of 
water, these masses increased in leathery hardness : green life 
was not extinct, but became feeble in colour, and too much 
changed to warrant further observations ; while a small por- 
tion, placed in another bottle and more freely exposed to the 
light, multiplied with great rapidity. Further observations 
were stopped by the declining strength of the plants. 
From the observations of the Rev. Mr. Osborne, on Closte- 
rium lunula, published in the * Quarterly Journal of Micro- 
scopical Science,' I should feel no doubt that the advancing 
motion in Cosmarium was also caused by cilia, the two families 
bearing a close resemblance to each other in their habits. 
Many careful observations made on Closterium, as detailed in 
the ' Annales des Sciences Naturelles,' vol. v., 1836, have been 
verified here in Cosmarium, though I am inclined to differ on 
the subject of the development of the sporangium. This body 
would appear to me to be the winter-casing of a large number of 
young plants, which escape from it by rapidly knocking against 
its walls when these have been loosened by spring warmth, 
or which grow up as the walls gradually decay in the midst of 
those gelatinous masses previously described. In proof of 
this opinion, 1 would adduce the immense increase in the 
number of the plants in the springs of 1852 and 1853, in 
some measure to be attributed to subdivision, as could be 
seen by the empty double cases figs. 14 and 21, but yet 
trifling as compared with the masses, of which figs. 31, 32, 
and 33, give only a faint idea. Why should such rapid 
