304 Philips on a Comparative Study of the 
protoplast lays down a dense wall which protects it through- 
out the resting period. The spore wall ruptures when the 
conditions favorable for growth are restored at the close of 
the resting period, and the protoplast pushes out, dividing 
as usual (Fig. 45). 
Another method of multiplication by spore formation was 
observed upon one occasion. At the time in question, while 
preparing a life-slide for the continuous observation of 
Oscillaria, a trichome of unusual appearance came into the 
field of the microscope. The end, or cap, cell, from which the 
finger-like hairs were protruding, was in place (Fig. 47),and 
the third cell was perfectly normal, apparently having given 
up none of its chromatin as in spore formation. The cell 
between these two, however,—the second cell of the fila- 
ment,—had every appearance of a spore with the exception 
of the heavy wall. The trichome was actively moving for- 
ward, which is not the case in plants that are forming, or 
have formed, spores in the manner described above, the 
cilia having been withdrawn and the end hairs absorbed. 
While observing this trichome, the end cell and the adja- 
cent enlarged spore-like cell separated from the rest of the 
filament and moved away slowly by means of the slow 
crawling movement of the finger-like processes. These pro- 
cesses were finally absorbed (Fig. 46), and the spore-like 
cell began to divide, the dense, diffused, nucleus-like centre 
separating into halves (Fig. 46) and a dividing wall grow- 
ing between them. Division continued until a six-celled 
stage was reached, by which time the cilia were formed and 
it could swim about freely in the water of the life-slide. On 
account of these movements it could no longer be kept under 
constant observation, but development had progressed far 
enough to show that it was forming into a new trichome. 
In Cylindrospermum the process of spore-formation is 
somewhat different, but follows the same general lines. 
Usually the end cell of a filament which has no heterocyst 
becomes strongly chromatic, probably through the chroma- 
