THE BEGINNINGS 01 LIFE. 435 



seasons or when exposed to different amounts of light 

 and heat, he was compelled to acknowledge that the 

 causes of these differences lay wholly beyond our powers 

 of observation. However much such facts might seem 

 to be contradicted by generally- received theories. 

 Dr. Gros, like a true student of Nature, said : — ^ Les 

 theories peuvent avoir leur valeur, mais elles doivent 

 servir a illuminer la serie des faits, sans nous eblouir 

 ni nous aveugler.' And yet Dr. Gros has, for the most 

 part, been referred to as a visionary and misguided 

 investigator, by critics who have immorally thrown 

 doubt upon the truth of his statements — they, at the 

 time, being almost wholly swayed by mere theoretical 

 considerations. 



Although my own observations upon Euglense have 

 been conducted during the months of January, February, 

 and March, and therefore at a period of the year which 

 is not very favourable either for obtaining large speci- 

 mens or for the occurrence of the higher kinds of trans- 

 formations, these observations have nevertheless, as 

 far as they have gone, tended in almost all respects 

 to confirm those of Dr. Gros. In many respects, 

 also, the changes which the Euglen^ pass through are 

 analogous to the transformations already described as 

 occurring in Nitella, Vaucheria, and other Algse. 



I shall commence with a description of the processes 

 of Analytic Heterogenesis which have been observed 

 to take place in Euglena;, and shall subsequently speak 



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