1877.) Reproduction in Fresh- Water Alge. 521 
bers of which are always in motion, and for this reason have often 
been classed in the animal kingdom. Figure 92, a, gives an en- 
larged view of a Volvox, which has the general appearance of a 
sphere studded over with a multitude of bodies arranged at quite 
regular distances and provided with two cilia. An enlarged view 
of a section of the outside of one of these spheres, with two of 
these ciliated bodies, is shown at b. Each of these bodies is con- 
sidered an individual, and therefore the whole sphere is, like an 
oak-tree or grape-vine, a community of individuals. Asexual re- 
production takes place by one or more of these individuals increas- 
ing rapidly in size and their contents dividing up into what are 
to develop into new individuals, forming thus a number of young 
communities within the old one, several of which are shown as 
dark, round bodies in a. When these young spheres have at- 
tained considerable size (c) they escape and become free and in- 
dependent colonies. ‘The succession of generations of motile 
families is brought to an end by the formation of resting spores. 
The separate primordial cells of the last motile family lose their 
cilia, and surround themselves with a firm, closely adherent cell- 
wall. They accumulate at the bottom of the water, and there 
grow into large green balls, the color of which passes over when 
mature into red. Only when these resting cells have remained 
dry for a long time are they in a condition when again moistened 
to develop gradually generations endowed with motion. The 
sexual reproduction is brought about in this family by the gelat- 
inous envelopes of the young families softening and setting free 
the separate cells, which move around by means of their cilia, 
When two of these cells meet they coalesce into a single body, 
the spore, which germinates and produces a new community after 
a period of rest.” 
Members of the genus Cidogonium grow frequently in stagnant 
Pools and are not very attractive to the naked eye, though when 
viewed through the microscope they become objects of interest 
to many. Their somewhat complicated methods of reproduction 
are given so clearly by J. Sachs, in his Text-Book of Botany, that 
We cannot refrain from using his language in describing them, as 
well as copying the plate which he uses from Pringsheim. “ ‘The 
reproduction of the (Edogoniex takes place by asexual swarm- 
Spores and by odspores produced sexually. An alternation of 
Senerations takes place in the following manner: From the 
spores which have remained at rest for a considerable period, 
Several (usually four) swarm-spores are immediately formed, 
