PROTOCOCCACE, 37 
adult Hydrodictyon. The primary cell wall now becomes more and 
more gelatinous, and soon undergoes complete solution, so that the 
new frond is set free in its native element. 
“It is evident that when the species is multiplied in the way just 
described the birth of the new frond is consentaneous with the death 
of the old cell. But when the Hydrodictyon disappear in the fall, it is 
months before they reappear in the spring. It is, therefore, evident 
there must be some other method of reproduction. This slow develop- 
ment of new fronds takes place, according to Pringsheim, by means 
of little motile bodies which he calls Dauwerschwarmer, which has been 
translated in English Chronispores (statospores, Hicks). M. Braun stated 
already some years since that sometimes, instead of the Hydrodictyon 
producing the ordinary reproductive bodies (macrogonidia), there are 
formed in the cells much smaller and more active bodies, the micro- 
gonidia. The changes which occur in the production of these are very 
similar to those already described ag happening when the macro- 
gonidia are formed. When the chronispores are formed, however, they, 
instead of uniting together, escape in a free, distinct condition with 
the water. They are now small ovate bodies, with a large anterior 
transparent space, to which are attached a pair of cilia, and their life 
and history, according to Pringsheim, is as follows:—Fora few hours 
they move abont very actively in the water, and then, dropping their 
cilia, and acquiring an outer cellulose wall, pass into a quiescent stage, 
in which they closely resemble Protococcus granules. They are capable 
of living in this state for a long time if kept in water. They can also 
endure dessication if the light be excluded during the process, but if it 
be present, they wither and die, and cannot be revivified. 
“ After a longer or shorter period, but never shorter than three months, 
according to Pringsheim, they recommence their life, provided they be 
in water. For four or five months after this the chief change consists 
simply in an increase in size. The dark green protoplasm is arranged 
around: the exterior of the cell; within are the more fluid colourless con- 
tents, the whole body still looking like a Protococcus cell. After a size 
of about {5th mm. is attained, the endochrome divides successively into 
several portions, The external layers of the surroanding wall now give 
way in some spot, and allow the inner layers to protrude and form a sort 
of hernial sac, into which the several endochrome masses soon pass, at 
the same time assuming the well-known characters of true zoospores. 
From two to five of these bodies are thus produced out of each original 
microgonidium. They are large, ovate, biciliate, and, generally, soon 
escaping from the hernial sac, move about actively in the water for a 
few minutes. Sometimes, however, they settle down within the genera- 
tive utricle. In either case, after a little time, they become motionless, 
lose their cilia, and develop into polyhedral cells, which are structurally 
remarkable for having their angles prolonged into long, horn-like ap- 
pendages. Under favourable circumstances, at the end of a few days, 
the bright green endochrome of these undergoes similar changes to 
those described as presaging the production of the microgonidia, and is 
finally formed into zoospores, which, in from twenty to forty minutes, 
unite, within the polyhedron or large cells, into Hydrodictyon, which is 
finally set free by a solution of the cellulose coat of the polyhedron. The 
network thus formed differs in no essential way from that which arises 
in the better known way, except that it is composed of much fewer cells. 
It is generally a closed sac ; but when the polyhedron, out of which it is 
developed, is small, it is sometimes merely an open network. Itsafter- 
history appears to be identical with that of the ordinary Hydrodictyon 
frond.”—Dr. H. C. Wood, ‘ American F. Water Alga.” 
Gq 
