OF MICRO-ORGANISMS. 57 



stout envelope; each member remains free in action, 

 and projects its two flagella through the cuticle. 

 With the Eudoryna elegans, the colony is modeled 

 upon nearly the same plan excepting that it is com- 

 posed of thirty-two individuals and that the latter, 

 placed beneath the same cuticle at equal distances 

 apart, do not touch one another. 



In the genus Volvox, colonies are found of which 

 the structure is very complicated. Such are the great 

 green balls formed by the aggregation of diminutive 

 organisms, which form the surface of the sphere, and 

 are joined together by their envelopes; they have each 

 two flagella, - which pass through the enclosing mem- 

 brane and swing unimpeded on the outside; the en- 

 velopes, each tightly holding the other, form hexag- 

 onal figures exactly like the cells of a honeycomb. 

 Each Volvox is at liberty within its own envelope; 

 but it projects protoplasmic extensions which pass 

 through its cuticle and place it in communication 

 with its neighbor. It is probable that these proto- 

 plasmic filaments act like so many telegraphic threads 

 to establish a network of communication among all 

 the individuals of the same colony; it is necessary, in 

 fact, that these diminutive organisms be in communi- 

 cation with each other in order that their flagella may 

 move in unison and that the entire colony may act as 

 a unit and in obedience to a single impulse. The 

 number of micro-organisms constituting a Volvox 

 colony is quite considerable: as many as 12,000 have 

 been counted. 



It was upon analogous phenomena that Gruber 

 based the existence of a diffused nervous system in 

 the Stentors. The same line of reasoning may be fol- 

 lowed in the case of the Volvox. Since unanimity of 



