IV PREFACE. 



mals here described liave been altogether ignored. For 

 equally obvious reasons, the peculiarities which are con- 

 nected with internal structures have been in many cases 

 passed over in silence, or merely alluded to ; whilst atten- 

 tion has been directed to the conspicuous characters 

 which are afforded by external points of structure. 



The animals selected as representatives of the various 

 classes are, with few exceptions, common types ; and any 

 teacher may readily obtain all of them, or nearly allied 

 forms, for class demonstration, so that all the more im- 

 portant points alluded to can be shown to the learner 

 upon the specimens themselves. 



The technical terms employed in the descriptions of 

 the types are exceedingly few in number, and explana- 

 tions of their meaning have been invariably inserted in 

 the text, along with their derivation, thus rendering a 

 separate glossary unnecessary. 



With the exception of the forms here chosen as repre- 

 sentatives of the classes of the Pteropoda and Brachio- 

 poda, the author may be permitted to state that he has 

 personally examined and dissected, either in the fresh 

 state or as preserved in alcohol, all the types here 

 selected for description ; and that in the cases excepted he 

 has a similar personal acquaintance with forms closely 

 allied to the ones described, whilst the latter have been 

 studied by him as regards their hard parts. Since most 

 of the forms here selected are of common occurrence, and 

 since the author is by profession a teacher of Natural 

 History, he does not state this as being in the smallest 

 degree a fact worthy of praise, or, indeed, of mention at 

 all in an ordinary way, but simply as a guarantee that he 

 is not merely retailing second-hand information. Most 

 of the facts, therefore, recounted in the present work, 

 though by no means original, have been verified by the 

 personal examination of the author ; and the descriptions 

 have been drawn from actual specimens. 



