ULV^E. 



49 



emit a globule of particles which is supposed 

 to be their fry. This substance lengthens, and 

 branches, and again forms long hair-like threads, 

 similar to those from which it sprang. In the 

 green ditch-laver (Ulva buttata, or minima), by 

 the aid of the microscope, may be seen a num- 

 ber of green granules,- these, when separate 

 and loose in the water, have a rapid movement, 

 as if chasing each other. In time, two ap- 

 proach, and touch one another, then retreat, touch, 

 and retreat again ; then four combine to execute 

 the same movement ; and at last, the whole party 

 thus grouped in fours, dance together in seeming 

 confusion. After a time the motion ceases, and 

 they form the new substance known as Ulva* 



* Lindley's Botany. 



F 



