MOLLUSCA AND ECHINODERMA 43 



quite as specialized as those living now, and, sortie of 

 them (Lingula, Discina), even generically identical. The 

 demand for time to originate the group is quite as grasp- 

 ing as that of the others we have been considering. 



All the Classes of Echinoderma, except the Holo- 

 thurians, which do not possess a structure favourable for 

 fossilization, are found early in the Palaeozoic rocks, and 

 many of them in the Cambrian. Although these early 

 forms are very different from those which succeeded them 

 in the later geological periods, they do not possess a 

 structure which can be recognized as in any way primitive 

 or ancestral. The Echinoderma are the most distinct 

 and separate of all the Coelomate Phyla, and they were 

 apparently equally distinct and separate at the beginning 

 of the fossiliferous series. 



In concluding this imperfect attempt to deal with a 

 very vast subject in a very short time, I will remind you 

 that we were led to conclude that the evolution of the 

 ancestor of each of the higher animal Phyla probably 

 occupied a very long period, perhaps as long as that 

 required for the evolution which subsequently occurred 

 within the Phylum. But the consideration of the higher 

 Phyla which occur fossil, except the Vertebrata, leads to 

 the irresistible conclusion that the whole period in which 

 the fossiliferous rocks were laid down must be multiplied 

 several times for this later history alone. The period 

 thus obtained requires to be again increased, and perhaps 

 doubled, for the earlier history. 



In the preparation of the latter part of this address 

 I have largely consulted Zittel's great work. I wish also 

 to express my thanks to my friend Professor Lankester, 

 whom I have consulted on many of the details, as well as 

 the general plan which has been adopted. 



If the facts and arguments set forth in the address to 

 which you have done me the honour of listening be 

 sound, the naturalist need not fear for the result of this 

 attack upon the great theory which has been a light to 

 his path for nearly half a century. Natural Selection will 

 never be stifled in the Procrustean bed of insufficient 

 geological time. 



