40 SCIENCE PROGRESS. 



expect a considerable series of representatives in the fossil- 

 bearing strata. On the other hand, their simple structure 

 and their extremely rapid decomposition form weighty 

 reasons for expecting little, and it will be seen that those 

 Algae now exhibiting special adaptations of structure to 

 durability are precisely the groups of which representatives 

 are preserved to us. The Diatoms with their siliceous walls, 

 the calcareous Siphonecz and Corallinece, are the Algae about 

 which one would now be most inclined to prophesy on 

 grounds of structure that their remains are most likely to be 

 embalmed in the deposits now forming in the ocean, and 

 they are all of them in fact found in sediments of contem- 

 porary age. If we add the encrusted Characece as sharing 

 in the chances of preservation no violence will be done to 

 reasonable expectation. It is a very remarkable fact that 

 after the Augean labour of Nathorst and others the only 

 fossil Algae of any importance left to us belong to these very 

 groups. They are almost the only Algae of our present 

 seas of which the structure is rendered fairly permanent by 

 mineral encrustation during life. May we not legitimately 

 suppose that in past ages their less resistant companions, 

 organised as they are at the present day, suffered such 

 extinction as it may be presumed they now undergo? If, 

 however, we look more closely into the record our expecta- 

 tions will be enhanced of findinQ' other forms. 



The first fossil Alo-a exhibiting- structure and so furnish- 

 ing adequate claims to recognition appears in the Devonian 

 age, viz., Ncmatophycus of Carruthers, and (with the excep- 

 tion of the doubtful Pachytheca of the same age) it 

 stands alone. It was first described under the name of 

 Prototaxites by Sir William Dawson, who took it for the 

 wood of a Gymnosperm, but the subsequent examination of 

 it by Mr. Carruthers (4 and 5) dispelled this interpretation 

 and established its claims as an Alga. He placed it among 

 the SiphonacecB (especially Udoiece) and beyond doubt cor- 

 rectly. It is hard to see on what ground Solms-Laubach 

 suggests Fucacecz, since the great uninterrupted lumina of 

 the tubes and the fine lateral haptera or tenacula are 

 wholly inconsistent with the structure of any Fucaceous 



