Ixxxvi THE BEGINNINGS OF LIFE. 



products, Desmidise, Diatomacese, Zygnemise, and nearly all 

 the vesicular Infusoria, formerly named polygastric. ... As a 

 general rule, the smaller Euglence are unable to produce such 

 organisms as are derived from the larger ones ; but the 

 larger species, on the contrary, can give birth to almost all 

 the derivatives of the smaller forms. ... As to the large 

 species, it may be said, with mathematical certainty, that they 

 are the common matrix of almost all the known forms of 

 Infusoria, that they may act as the germs of certain plants, 

 that they produce, as side products, Closteriae, Diatomacese, 

 &c. ; that they can succeed in engendering almost all the 

 Rotifers or Systolides, that they can also give birth to Nema- 

 toids, Tardigrades, &c. . . . We are not here speaking about 

 theories, more or less logical, but only concerning facts 

 which every skilled observer may ascertain for himself, if he 

 has the good fortune to seize the Euglence at the time when 

 they begin to encyst themselves, or to undergo transforma- 

 tions at the surface of the water, where their juxtaposed 

 albuminous cysts form a very picturesque alveolar network 

 which may present different stages of metamorphosis, 

 more or less advanced.' Dr. Gros also believes that light 

 exercises a most important influence over the transforma- 

 tions ol EuglencE. Where it is absent their developmental 

 modifications rarely go on to the production of plants ; the 

 offspring under such conditions are rather animals of one 

 form or another. He has also come to the conclusion, after 

 numerous observations frequently repeated, that different 

 organisms spring from the same matrix according to the 

 mere quantity of matter entering into their composition — 

 though of course these variations may be also associated 

 with alterations in quality. He says: — 'To give one ex- 

 ample of this, out of many others, the substance of certain 

 Eugle7tcB becomes converted into a kind of Qgg, which has a 

 striking resemblance to the eggs of Nematoids. A certain 



