No. 461.] MOVEMENTS OF DIATOMS. 291 
end, the desmid will be raised to a vertical position and will take 
up oscillating or circular movements. 
If we now pass to a consideration of like movements in the 
Cyanophycez, the same explanation holds true for Oscillaria 
which often takes up a waving or circular motion when attached 
at one end. This movement is well described by Griffith and 
Henfrey ! as follows : “ The ends of the filaments emerge from 
their sheaths, the young extremities being apparently devoid of 
their coat ; their ends wave backward and forward, somewhat as 
the forepart of the bodies of certain caterpillars are waved when 
they stand on their prolegs with the head reared up." The 
authors attribute this motion to “irregular contraction of the 
different parts of the protoplasm.” 
The free-swimming species of Nostoc all have a spontaneous 
power of active motion in water, and in all of the filiform orders 
of the Cyanophycez, detached portions of the filament known as 
hormogones also have the power of spontaneous motion. All of 
these movements can be exactly duplicated with lithia tablets in 
water or with aluminum of the proper weight and shape immersed 
in strong caustic solution, and are also undoubtedly caused by 
the strong evolution of oxygen gas due to the activity of the 
chiorophyl present in the organisms. 
MT. PROSPECT LABORATORY, 
BROOKLYN, N. Y. 
1 Micrographic Dictionary, P- 561. 
