160 Herbert L. Hawkins — Studies on tlie Echinoidea, etc. 



v. morphological studies on the echinoidea holectypoida and 



their Allies. 



By Herbert L. Hawkins, M.Sc, F.G.S., Lecturer in Geology, University 

 College, Beading. 



Foreword. 



DURING- the past seven years I have published several papers 

 based upon preliminary investigations on the anatomy of the 

 Holectypoida, an order of the Euechinoidea which, by general 

 consent, is regarded as transitional between the Regular and Irregular 

 sections of the class. Continued study, aided by increased mental 

 and technical experience, has revealed an ever-increasing number of 

 interesting features in the order, and has made possible more definite 

 and confident surmises as to its affinities with other groups. The 

 series of contributions here commenced is intended to amplify, and in 

 some cases to correct, the statements made in my earlier papers. 

 With very few exceptions the actual descriptions that are given in. 

 the former work still seem to be essentially correct, but every fresh 

 examination, even of the same specimens, testifies to the incomplete- 

 ness of most of the observations hitherto published. New material, 

 better or differently preserved, often draws attention to features 

 overlooked or discarded as unimportant in the examples already 

 studied. No apology is needed for the publication of incomplete 

 descriptions of natural objects, since complete knowledge is as yet 

 nowhere attained. When inaccuracies of observation have been 

 detected, their nature and cause will be stated frankly, accompanied, 

 verbally or not, by suitable contrition. 



But in matters of theory — the tracing of phyletic series and of the 

 trend of structural evolution — the contrast between my present 

 views and those previously held and expressed is likely to appear 

 more marked. A structural feature overlooked or misunderstood 

 may be added to, or modified in, a description without seriously 

 altering the whole; but when the corrected knowledge is applied to 

 a theory, it may produce a veritable revolution. Nevertheless, if the 

 formulation and publication of theoretical conclusions were to be 

 postponed until a basis of complete knowledge is attained, science 

 would speedily sink into a state of encyclopaedic chaos, without so 

 much as an alphabetical classification in which to wrap its disjointed 

 facts. Much of the progress of science is achieved by reasoned 

 attacks upon established theories, and if it is legitimate and profitable 

 to demolish the flimsy edifices of others, it is surely less invidious 

 and more seemly to treat similarly the product of one's own 

 imperfect efforts. So that it will be with joy in the new and better 

 building, rather than with regrets and apologies for the earlier 

 erections, now obsolete and superseded, that the fresh theoretical 

 opinions will be raised. To suggest that the new theories are correct 

 in detail would be ridiculous, but they are more securely founded 

 than the former ones, and can yield place only to a better series, 

 based upon more complete knowledge. 



I have chosen the serial method of presenting my results, partly 

 on account of their bulk, and partly because the aspects of the 



