368 SCIENCE PROGRESS. 



opinion as to the facts they record. We are accustomed to 

 find in the petrified remains of Permo-Carboniferous plants 

 every detail of wall sculpture and cell outline faithfully pre- 

 served, but to have millions of examples of a gelatinous 

 alga with cells, and even cell contents, clearly defined, is a 

 revelation which borders on the miraculous. 



Have we sufficiently good evidence before us that the 

 boghead structures are really gelatinous algae ? Must we 

 look upon the bright, yellow bodies in these rocks as the 

 result of the phenomenon which we are familiar with on a 

 smaller scale in the breaking of the meres? In the first 

 place it may fairly be asked : Do the descriptions and figures 

 of Pila bibractensis show a marked resemblance to any 

 known form of alga ? Bertrand gives numerous drawings 

 of this species, showing what he believes to be different 

 stages in the development of the thallus. The general ap- 

 pearance of the structure does not suggest any distinct 

 resemblance to any type of recent plant, and it is difficult to 

 understand with what form of alga these Palaeozoic speci- 

 mens may be best compared. The existence of proto- 

 plasmic and nuclear substances in a fossilised condition, as 

 described by Bertrand and Renault in the case of the bog- 

 head structures, and by Lignier 1 in Bennettites, can hardly 

 be credited ; it is true we frequently find a black substance 

 in the secretory canals of fossil plants, but the preservation 

 of carbonised resins or gums is much more intelligible than 

 the mineralised remains of protoplasmic material. It is 

 hoped than an examination of boghead sections may lead to 

 a more definite expression of opinion on the nature of these 

 cellular structures, but at present it is very difficult to accept 

 the published results as to these minute yellow-coloured 

 bodies. Without venturing to speak at all dogmatically, 

 the more probable conclusion seems to be that we have here 

 to deal with curious inorganic structures which closely 

 simulate the cellular structure of plants. 



A. C. Seward. 



( To be continued. ) 



1 For notice of Lignier's excellent paper see Nature, p. 594, Oct., 1894. 



