412 THE BEGINNINGS OF LIFE. 



remain green. But, as Dr. Hicks says, c After a time 

 the old cell wall dissolves away, and then it becomes 

 evident that the contents have assumed the form of, 

 or rather, have become a Gleocapsa, which certainly 

 undergoes segmentation freely I have seen con- 

 siderable masses of Gleocafsa produced in this manner 1 .' 



But we have not yet mentioned all the changes 

 which chlorophyll vesicles or the ultimate elements 

 of Algas may undergo. They may even lapse into 

 modes of growth whereby Pediastrese, Desmids, or 

 Diatoms are produced. These remarkable metamor- 

 phoses were long ago pointed out by Dr. Gros, though 

 his statements on this subject (in common with many 

 others to which we shall subsequently allude) have 

 been almost universally disregarded. And yet the 

 paper in which his observations are recorded is pro- 

 bably one of the most important that has ever been 

 published on a biological subject. His statements were 

 made, however, whilst the minds of the majority of 

 naturalists were enthralled and whilst their vision was 

 perverted by mere theories so that they could neither 

 discover the truth for themselves nor give credence to 

 the positive representations of one who had been able 

 to approach the subject like a true student of nature. 



Dr. Gros' own words on the subject of the origin of 

 Desmids and Diatoms are as follows 2 : c En 1845, nous 



1 Loc. cit., PI. Iviii. fig. 24. 



2 Loc. cit., p. 339. And it must be remembered that Dr. Gros wrote at 

 a period when so much precision had not been given to the nomenclature 



