28 ON SOME TRACKS OF INVERTEBRATE ANIMALS. 



order that his representations of them should owe nothing 

 to the imagination of his artist, he employed photography, 

 that unerring delineator, in illustrating his memoir; an 

 example which I have followed on the present occasion. 



Examples of what are probably concretionary objects 

 occasionally occur of such a magnitude as to make it 

 improbable in the highest degree that they can have been 

 of vegetable origin. Some of these might be regarded as 

 a huge form oiDictyonema, in which the fibres forming the 

 network are six inches in circumference, and the enclosed 

 meshes a foot wide. At the junction of the lowermost 

 beds of the Coralline Oolite with the uppermost beds of 

 the Calcareous Grit at Filey Brig in Yorkshire, acres of 

 the contiguous surfaces of the two rocks are covered with 

 such a huge network of coarse inorganic sandstone, in 

 which the cylindric form is sufficiently perfect ; but after 

 prolonged study of these ramifying objects, all that 

 Professor Phillips could say of them is that '^^they are 

 ramified masses of doubtful origin, which appear like 

 dichotomous cylindrical sponges ^^"^. Thoroughly familiar 

 with these structures, I never for a moment doubted their 

 inorganic character. Such objects can have no weight 

 with the student of Evolution, and until we obtain more 

 definite proofs than we have hitherto obtained of the 

 vegetable nature of most of these dubious ^^ Palaeozoic 

 Algse,^^ we must reject their testimony when framing a 

 pedigree for the vegetable kingdom. At the same time 

 I regard the existence of an abundant marine vegetation 

 during the Palaeozoic ages as an inevitable corollary of 

 the fact that the rocks of those ages abound in the 

 remains of Phytophagous animals. But many sources of 

 error surround us when we endeavour to demonstrate 

 that existence by means of the anomalous objects which 

 those rocks have already supplied to us. 



* Geology of the Yorkshire Coast, 2ncl edition, p. io6. 



