174 THE SUCCESSION OF ANIMAL FORMS 



The Linguklla, whether we regard them as molluscoids, or, 

 with Professor Morse, as singularly specialized worms, represent 

 a peculiar and distinct type, handed down, through all the 

 vicissitudes of the geological ages, to the present day. Had 

 the Primordial life begun with species altogether inscrutable 

 and unexampled in succeeding ages, this would no doubt have 

 been mysterious ; but next to this is the mystery of the oldest 

 forms of life being also among the newest. One great fact 

 shines here with the clearness of noon-day. Whatever the 

 origin of these creatures, they represent families which have 

 endured till now in the struggle for existence without either 

 elevation or degradation. Here, again, we may formulate an- 

 other creative law. In every great group there are some forms 

 much more capable of long continuance than others. Lingula 

 among the Brachiopods is a marked instance. 



But when, with Hicks, we surmount the mass of barren beds 

 underlying these remains, which from its unfossiliferous charac- 

 ter is probably a somewhat rapid deposit of Arctic mud, like 

 that which in all geological time has constituted the rough fill- 

 ing of our continental formations, and have suddenly sprung 

 upon us many genera of Trilobites, including the fewest-jointed 

 and most many-jointed, the smallest and the largest of their 

 race, our astonishment must increase, till we recognise the fact 

 that we are now in the presence of another great law of creation, 

 which provides that every new type shall be rapidly extended 

 to the extreme limits of its power of adaptation. 



That this is not merely local is evidenced by the researches 

 of Matthew and Walcott in the oldest Cambrian of America, 

 where a similar succession occurs, but with this difference, that 

 in the wider area presented by the American continent we find 

 a greater variety of forms of life. Walcott records up to 1892 

 no less than 67 genera and 165 species in the oldest Cambrian 

 of America. These include representatives of the Sponges, 

 Hydroids, Corals, Echinoderms, Worms, Brachiopods, Bivalve 



