ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 325 



brancli in the same manner as before. In this way a whole tree is 

 produced. 



This manoeuvre is carried out by the worms, not merely on the 

 surface, but they also burrow into the mud and from a given point 

 produce a system of branched tubes, which being lined with a slimy 

 coating, acquire a certain firmness. If a thin mixture of plaster of 

 Paris be carefully poured over this perforated mud or clay, it will 

 enter the tubes, and by carefully washing off the mud after the plaster 

 is fixed, the cast of the tubes will bear the appearance of a delicate 

 tree. 



If it is assumed that a bed of mud or clay can be thus burrowed 

 by Goniada and Glycerea, and that the biu'rows can be filled with a 

 soft substance, there will consequently be seen in a section of this 

 bed, branched impressions which have the appearance of Algfe, but 

 which are, in reality, branched tubes made by worms. 



With regard to the fossil Chondrites, especially Chondrites hollensis 

 and hechingensis, and the Chondrites of the Flysch, it had already 

 occurred to many that these so-called Fucoids did not lie, like other 

 fossil plants, pressed flat between the strata, but that they were found 

 much more nearly in their proper form in the beds of marl, as though 

 they had grown through them. It was also remarkable that they 

 were never found in a carbonaceous condition, but invariably in marl. 

 Heer has also drawn attention to the fact that these ' Fucoids ' occur 

 in all formations, from the lias to the upper eocene, in almost 

 identical forms, while in existing seas hardly any analogous specimens 

 can be found. This fact was the more inexplicable when it was con- 

 sidered that, for example, the algae of the Paris limestone, or the 

 Flysch of Monte Bolca bore the closest resemblance to the existing 

 forms of algfe, so that at the period of the eocene formation, types 

 of algae existed analogous with the present. 



There were also other difficulties. Algfe always grow only in 

 small depths on a firm foundation, and never in mud. Now the 

 localities in which the so-called Fucoids are found in the greatest 

 quantities are manifestly formations of mud, and deposited in a deep 

 sea.* 



All these difiiculties at once vanish when it is kno"s\Ti that these 

 so-called ' Fucoids ' of the Flysch are not algfe, but only the tracks 

 of worms ; the peculiarity of their origin is then no longer incom- 

 prehensible. Worms are to be found in the sea at a great depth, 

 and like especially slime and sand ; and it thus becomes evident that 

 such perishable impressions as those made by worms are more lasting 

 in the deep sea than in the formations nearer the shore, because they 

 are not so easily effaced or disturbed. 



Among other marks observed by Nathorst, the following may be 

 mentioned : — CorojpMum longicorne (a Crustacean) makes an impression 



* It might of course be assumed that algse, like Sari/ussuin, torn from the 

 place ^yhere they grew, and driven out to sea, fiually sink down into tlie mud of 

 the deep sea, but even with such an hypothesis these Algae would always appear 

 miusual and accidental, while the Chondrites in the Flysch have a constant 

 characteristic. 



