72 MYRIAPODA 



minute anatomical examination showed us that this difference 

 was not so great as appeared at first sight, the cord showing 

 traces of a duplication. Well, are these traces superficial, or do 

 they represent a state of affairs more or less similar to that in 

 the Chilopoda ? Embryology helps us to answer this question 

 also. In the early stages of the Chilognatha we find that the 

 nerve cord has exactly the form of that in Chilopoda, showing us 

 that the appearances in the anatomy had led us to a right con- 

 clusion, and giving us a valuable confirmation of our views. 

 These two examples will serve to show the kind of interest 

 which attaches to embryology. 



Palaeontology. 



We have seen that embryology enables us to look at the 

 structure of the Myriapods from a new standpoint, and to correct 

 and supplement the knowledge gained from an examination of 

 the adult animal. In the same way a study of the forms of 

 Myriapods which have become extinct on the globe, and have 

 been preserved to us in a fossil form, gives a further opportunity 

 of considering the relations of one form to another, and again of 

 the relations of our group to other groups of animals now exist- 

 ing on the earth. Myriapod fossils have been found in strata of 

 great antiquity. The oldest of such fossils must have been 

 among the first land animals. The figure below shows a fossil 

 Myriapod found in America, belonging to the Order of the 

 Protosyngnatha which are only found in the Palaeozoic strata. 

 It is a good example of the manner in which Myriapods were 

 protected by bundles of bristles in the same way as the 

 Polyxenus of the present time. 



The oldest fossil Myriapods which have been discovered at 

 the present time are two species which have been found in the 

 Old Bed Sandstone in Scotland. To realise the antiquity of these 

 Myriapods, it will be worth while recalling the typical fossils 

 found in the Old Eed Sandstone, so as to see what the contem- 

 poraries of these ancient Myriapods were like. Among the plants 

 there were Algae, Ferns, and Conifers, belonging to the lower 

 divisions of the plant tribe. Among the animals there were 

 Sponges, Corals, Starfish, Worms, Shell-fish, and Pishes, but none 

 of the more highly organised of the animal or vegetable tribe 



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