PREFACE. 



accurate observation, and sound judgment. During 

 the preparation of this work I have had the benefit of 

 his valuable opinion in many cases of difficulty, and 

 have often been materially assisted by his cautious 

 wisdom and remarkable skill in the discrimination of 

 species. His collection was freely placed at my ser- 

 vice ; and many of the figures with which this work is 

 enriched are engraved from his admirable drawings. 



To Mr. Busk I am under peculiar obligations for 

 much valuable counsel and practical aid, and especially 

 for his kindness in placing at my disposal his large 

 and interesting collection of foreign Hydroida and an 

 extensive series of drawings. 



To my friend Prof. Allman I owe my warmest 

 thanks for the readiness with which, out of his large 

 stores of knowledge, he has communicated informa- 

 tion that I happened to need, or favoured me with 

 his views on doubtful points. I am also indebted to 

 him for drawings of some of the species which he has 

 discovered. The reader of this work will understand 

 how much I, in common witli all zoophytologists, owe 

 to his writings. 



Dr. Stre thill Wright has rendered me most impor- 

 tant service by permitting me to reproduce the figures 

 which illustrate his valuable papers, and by freely 

 communicating to me his views on some of the most 

 interesting questions in zoophytology. 



To the Rev. A. M. Norman I am indebted for the 

 use of the late Mr. Barlee's collection of Hydroida, 

 including many Shetland acquisitions, and for the 



