324 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tlie known structure of the chloropliyll-bodies of plants ; and those 

 who, like Semper and Brandt, have supposed them to bo parasites, 

 have been misled, first by an imperfect acquaintance with the character 

 of chloroiihyll-bodies in general and of these in particular, and 

 secondly by the plausible but delusive analogy presented by the 

 " yellow-cells " of liadiolarians and of Authozoa. 



There is a field for experimental inquiry in regard to animal 

 chlorophyll, as it is very important to know whether it serves the 

 same purpose as in the plant, and if so, whether we may not bo able 

 to get indications as to the disputed function of the green pigment 

 which plants are unable to furnish. 



Falaeontological Significance of the Tracks of Different In- 

 vertebrates. — Herr Nathorst has instituted some very interesting 

 and important experiments in explanation of the traces in rock 

 formations of various organisms. As we have not the original, we 

 give the following report on it by T. Fuchs : * — " In the sandstone 

 and marl of all formations there are often found, in greater or less 

 quantities, certain marks and imjn-ints the nature of which has been 

 hitherto problematical, as they have been interpreted either as algSB 

 or animals, or simply regarded as inexjjlicable. Such are the Fucoides 

 Harlani from the Cambrian of America, the Nemeriites of the culm- 

 shales, the ' Zopfjplatten ' (a term ajiplied to flattened hair-like 

 impressions) of the Jura, the endless varieties of different ' hiero- 

 glyphs ' of the Flysch formation, as well as the various impressions 

 described as Prolichnites, Eophyton, Spirophyton, Taonurus, &c. 



Nathorst has hit upon the happy idea of solving this problem by 

 allowing diiferent animals to crawl or run over soft mud, and then 

 studying the tracks thus made by them. Although he has only 

 experimented with about 40 marine animals, and a few insects, larvaa, 

 and earth-worms, still the result of his researches was truly astonish- 

 ing, as he succeeded not only in artificially representing the finest 

 Nemertites, Harlanice, ' Zojjfplatten,' Eophyton, &c., but he made the 

 most unexpected discovery, that by far the greater number of the 

 so-called ' Fucoids ' (e. g. Bufhotrephis, Chondrites hollensis, Ch. 

 hechingensis, and even the Fucoids of the Flysch, are nothing else 

 than branched worm-tubes. However unex2^ected this discovery may 

 be, there can hardly exist a doubt as to its accuracy after the experi- 

 ments and evidence of the author. On taking several worms of the 

 species Goniada and Glycerea, which are found in great numbers on 

 the coasts of Norway, and allowing them to crawl over soft mud, he 

 observed, to his astonishment, that they invariably made a branched 

 track, like the twigs of a tree. They first advance a short distance, 

 then go back a little over the track, and turn away on one side, thus 

 jiroducing a branch ; this they repeat from different points and on 

 different sides, finally returning to the point whence they started, 

 and make a second main track in another direction, which they 



* llandl. K. Svenska Vetens. Akad., xviii. (1881). Verb. k. k. Geol. 

 Etichsaiist., 1881, p. 34G. Sec Naturforscher, xv. (1882) pp. 113-16. 



