APPENDIX D. Ixxxv 



According to Dr.G.Gros 1 , Eughnce. and Astasia are protean 

 creatures of variable size which undergo the most remarkable 

 metamorphoses. They are capable of giving birth to very 

 varied forms, such as one would scarcely be able to refer to 

 their real origin, if the various transitional stages had 

 escaped observation. These organisms are almost univer- 

 sally distributed, and are capable of giving rise both to 

 animals and plants, under the influence of varying sets of 

 external conditions. Of specimens obtained from the same 

 source, though placed under different conditions, one half 

 may develop into animals, and another half into plants. 

 Dr. Gros says : ' When millions of Euglenae taken on the 

 same day from the same locality, metamorphose themselves 

 after a certain fashion in one vessel, and after a different 

 fashion in an adjacent vessel, one cannot but place faith in 

 the results, even though one has not actually witnessed [all 

 the steps of] these unaccustomed, though obvious changes 

 in which there is no room for error, since the transformations 

 take place generally within cysts into the midst of which 

 one could not suspect the introduction of foreign organisms. 

 . . . Why should certain specimens of Euglence follow one 

 mode of change rather than another ? Why, at the firs;; 

 transformation, do they sometimes attain a degree of de- 

 velopment to which others arrive only after successive trans- 

 formations ? I know nothing concerning this ; but that such 

 phenomena do occur, I am certain. . . . Euglence may, on the 

 one hand, chance to produce Confervae and Mosses; on the 

 other, they may give origin to Rotifers, Nematoids, Tardi- 

 grades, &c., according to their size, and to the circumstances 

 in which they are placed that is to say, according to the quan- 

 tity and the quality of the substances which they assimilate. 

 ... In the course of their metamorphoses, they sow, as side 



1 'Ann. des Sc. Nat.,' 3 Sr. t. xvii. 1852, p. 193. 



