No. 444.] PTERASPID& and cephalaspid^e. 



829 



derms, were annectant types uniting the true fishes with the 

 arthropods, and possessing some of the characters of both 



I raised the question in iSSg. in my fust paper "On the Origin 



primarily on the microscopic structure of the head shields, the 

 presence of fish-like scales in Pteraspis, and of a caudal fin in 

 Cephalaspis. Their authoritative opinion settled the question 

 for the time being, and soon afterwards, the almost universal 

 belief in the derivation of vertebrates from soft bodied annelid 

 ancestors that would leave little or no trace behind, and the wide- 

 spread conviction that the growing science of embryology was 



lems, turned the attention of morphologists away from the pale- 

 ontological aspect of the problem. 



The development of new lines of zoological research and the 

 failure of embryology to realize the over confident expectations 

 of its disciples, as well as the frequent and flagrant abuses of 

 embryological data, haw produced within the last decade a spirit 

 of impatience, or of indifference, towards phylogenetic specula- 

 tions in general and a reaction set in, not only against the 

 annelid theory of the origin of vertebrates, but against all 

 theories that attempt to bridge this, the widest gap in the whole 

 organic kingdom, bv a purelv speculative use of embryological 

 data. 



The association of such names as Hugh Miller, Louis Agassiz, 

 Huxlev and Lankester with the earlv history of Pteraspis and 

 the Cephalaspida- adds greatly to the interest that has long 

 centered in this group. 



In Siluria, (London 1854, p. 252), Sir Roderick I. Murch- 

 ison speaking of Cephalaspis agassizii says : This fish with its 

 large buckler-shaped head and its thin body, jointed somewhat 

 like a lobster, is perhaps the most remarkable example of a fish 

 of apparently so intermediate a character, that the detached por- 



