AND THE LOWER ANIMALS. 187 



Comparing the writings of Pineau,* Pouchet,t and 

 Stein^J and admitting that the facts npon which these 

 observers agree are true,, we are led to regard the 

 changes of form as exceedingly numerous. If we 

 associate some of these with the facts announced by 

 Jules Haime,§ we shall see that these alterations are 

 still more numerous, and the Infusoria may be then 

 considered the group in which the metamorphoses 

 which a single species may undergo are carried to 

 their greatest length. Such in fact was the opinion 

 I myself put forward when first engaged in the study 

 of these complex questions ; but later discoveries, and 

 especially those of Claparede, Lachmann, and Balbiani, 

 induced me to modify it. 



Have not the two first writers whom I have men- 

 tioned gone into the other extreme ? According to 

 them, the metamorphoses of ciliated infusoria in 

 general are most probably of a very simple character. 

 The embryo, which is not very unlike the parent, has 

 to undergo but slight modifications in acquiring its 

 definitive form.|| This conclusion is at all events a 

 premature one. It is based exclusively upon a very 



* " Annales des Sciences naturelles," 1845 — 1848. 



f " L'Institut," 1849. 



J Stein's first writings date from 1849 ; they appeared in various 

 German magazines, and were in part reproduced in the "Annales 

 des Sciences naturelles." 



§ " Observations sur les Metamorphoses et 1' Organisation de la 

 Trichoda lynceus (A spidisca lynceus, Ehrenb.)." — Annales des Sciences 

 naturelles, 1853. 



|| The transformations of the Acineta embryos have been all 

 observed by Cienkowski, Claparede, Lachmann, and D'Udekem ; 

 but none of these writers have extended the same form of researches 

 to the other groups (" Etudes sur les Infusoires"). 



