VOLVOCINE^E ; PALMELLACE^E 557 



becomes an irregular mass of colourlsss protoplasm, containing a 

 number of brown or reddish-brown granules, and capable of altering 

 its form by protruding or retracting any portion of its membranous 

 wall, exactly like a true Amoeba. By this self-moving power, each 

 of these bodies (of which twenty may sometimes be counted within 

 a single Volvox) glides independently over the inner surface of the 

 sphere among its unchanged green cells, bending itself round any 

 one of these with which it may come into contact, precisely after 

 the manner of an Amoeba. After the 'amoeboid' has begun to 

 travel, it is always noticed that for every such moving body in the 

 Volvox there is the empty space>of a missing cell ; and this confirms 

 the belief founded on observation of the gradational transition 

 from the one condition to the other, and on the difficulty of sup- 

 posing that any such bodies could have entered the sphere parasiti- 

 cally from without that the * amoeboid ' is really the product of the 

 metamorphosis of a mass of vegetable protoplasm. This meta- 

 morphosis may take place, according to Dr. Hicks, even after the 

 process of binary subdivision has commenced. What is the sub- 

 sequent destination of these amoeboid bodies has not yet been ascer- 

 tained. 1 



In other organisms allied to Volvox, and included in the family 

 Volvocineos, we find a very interesting and instructive transition 

 between the various modes of multiplication already described. In 

 Eudorina, a common organism in still water, a sexual process similar 

 to that in Volvox has been observed. In Pandovina inorum the 

 generative process is performed, according to the observations of 

 Pringsheim, in a manner curiously intermediate between the lower 

 and the higher types referred to above. For within each cell of the 

 original sixteen of which its mulberry-like mass is composed, a brood 

 of sixteen secondary cells is formed by ordinary binary subdivision ; 

 and these, when set free by the dissolution of their containing cell- 

 wall, swim forth as 'swarm-spores,' each being furnished with a 

 pair of flagella. Among the crow r d of these swarm-spores may be 

 observed some which approach in pairs, as if seeking one another ; 

 when they meet, their points at first come together, but gradually 

 their whole bodies coalesce, and a globular zygospore is thus formed 

 which germinates after a period of rest, reproducing by binary 

 subdivision the original sixteen-celled, mulberry-like Pandorina. 

 We have here, therefore, a true process of conjugation between 

 motile protoplasm masses, each of which is in itself indistinguish- 

 able from a zoospore. A similar process takes place also in 

 Conferva, Ulothrix, Hydrodictyon, and a number of fresh-water algae 

 (fig, 422). 



Included by many writers under the general term Palmellaceae 

 are a number of minute organisms of very simple structure, the 

 relationship of which to the Protococcacece is not yet fully known. 

 They all grow either on damp surfaces or in fresh water ; and they 

 may either form (1) a mere powdery layer, of which the component 



1 A similar production of ' amceboids ' has been observed by Mr. Archer in 

 Steplianosplicera pluvialis, and is scarcely now to be considered an exceptional 

 phenomenon. 



