PREFACE. IX 



And of foreign naturalists, personally unknown to 

 him, he would especially single out, for courteous 

 thanks, Professors Gregenbaur, E. Leuckart, Milne 

 Edwards, and Agassiz. 



To Mr. Grosse the Author is indebted for the 

 loan of the beautiful drawings from which two of 

 the woodcuts have been copied. The wood-en- 

 graver, Mr. William Oldham of Dublin, has exe- 

 cuted his share of the following pages in by no 

 means an unsatisfactory manner. 



Mr. Busk, the Eev. Thomas Hincks, and Dr. 

 Strethill Wright have also supplied the Author 

 with some valuable facts touching the structure of 

 the fixed Hydrozoa. 



Queen's College, Cork ; 

 April, 1 86 1 



August, 1 861. 



Professor ]Max Schultze has just published a 

 memoir on Hyalonema in which he confirms the 

 opinion that the beautiful siliceous fibres of this 

 organism are, in truth, to be regarded as spicules 

 of a Sponge, allied, in some respects, to Euplec- 

 tella. 



Very recently. Professor Agassiz (op. cit. (71) 

 p. 256), from personal examination of the living 

 animal of Millepora, has concluded that the 



