On Problematic Organ 

 1 that the probability 



Alga 



algre in a fossil state, much can be said. It will perhaps not 

 be denied by any geologist, no matter to which one of the two 

 schools he may belong, that alga' must have existed through- 

 out all geological time, and that, too, often in the greatest 

 abundance. This lias been insisted upon by Salter (Memoirs 

 of Geological Survey of Great Britain, vol. 3, 1860): by Les- 

 quereux in his various publications (2nd Geological Survey of 

 Pennsylvania, Report J : also Coal Flora, Report P; 13th An- 

 nual Report Geological Survey of Indiana; Annual Report 

 Geological Survey of Pennsylvania for 1886, etc.), and by 

 others. The presence of masses of graphite in the Laurentian 



say nothing of the mere fact that myriads of animal forms 

 could not have existed without the presence of alga?, is suffi- 

 cient proof that they once existed. Rut the questions are: 



preservation? Are all the forms that have been described as 

 alga', really such? If not: to what can they be referred? 

 What is their origin ? The answer to some of these questions 

 is final as regards certain of the problematical organisms : but 

 the answer to the first two general questions has certainly not 

 yet been given. 



The opinion held by many students is frequently biased by 

 the expressed opinion of the first observer or describer of a 



