VI I'UKI'ACK. 



completed the description of all the species even in the 

 first genus, AxriiUti; there being blanks in the MS. in- 

 tended to be filled up, and these gradually become more 

 frequent ; while the pelagic forms, Shilpa, Pyrosoma, 

 Appendicularia, &c,, are not treated of at all. But 

 the fixed forms frequenting our shores are of most 

 general interest, at least to the amateur naturalist, 

 and this account of them renders fairly easy the 

 identification of the species known at the time the 

 authors Avrote. Since then others have been dis- 

 covered, and the classification and nomenclature of 

 the Tunicata have been much altered. Even their 

 position in the Animal Kingdom has been raised 

 from the invertebrate Molluscoidea to the degenerate 

 pseudo-vertebrate Urochordat a, a Class of the (Jhordata 

 formed for their reception. 



In the preparation of the first two volumes I had 

 the advantage of the much valued assistance of Canon 

 Norman, and I greatly regret that owing to failing 

 health he has been unable to continue that assistance 

 with the present volume. To him \ve owe the 

 appearance of the work which throughout bears 

 evidence of his assiduous collecting, the material 

 supplied by him being far more extensive than that 

 contributed bv anv other of the authors' friends, 



t / i t 



and in the number of new species surpassing even 

 their own collections. His portrait, by my request to 

 him, forms the frontispiece to this volume. 



When I commenced the preparation of the mono- 

 graph I intended to add to the concluding volume a 

 Bibliography of the Tunicata, but that has so greatly 

 exceeded its anticipated extent that it must appear as 

 a separate volume, a necessary adjunct, however, to 

 the monograph on account of the abbreviation of the 



O 1 



titles of works quoted in it. 



JOHN HOPK1XSOX. 



WEETWUOD. WATFORD, 



oOth December, It'll . 



