71 



tlie Hjdroida has long been iii great part obsolete, while the uuiubeis of 

 kuowa species has been almost trebled since he wrote. Like his predeces- 

 sor, Ellis, he rendered in his day invaluable service to Zoojiljytology, and 

 i:ave an iopulse to the study of it of which we are now reaping the fruits. 

 It. should be added that there is a charm in his work which does not become 

 obsolete with its science; it will always rank with the ' Corallines' of Ellis, 

 amongst the classics of Natural History I'terature. As a manual for the 

 use of the student, however, it has long ceased to be of any value ; nor is 

 there any work in existence that contains a complete account of the British 

 Ilydroida. The place, therefore, is vacant which the present work ai^pircs 

 to fill. I have endeavoured to make it a full and faitliful ex])ositiou of our 

 present knowledge, and to do for students of this day what Johnston's his- 

 tory accomplished for those of his own generation. It is certainly lime that 

 the remarkable results attained since lie wrote, and now widely scattered, 

 should be presented in a connected form, and made availal>le for general 

 use; and that the diiBculties should be removed which interfere with the 

 cultivation of one of the most delightful branches of Natural History. 



The enormous advance that has been made in our know- 

 ledge of the structure and life-history of the Hydrozoa gene- 

 rally within the last few years^ has necessarily led to wide 

 and sweeping changes in their classification, and in no divi- 

 sion of the class has this advance been greater, nor the 

 necessity for an improved nomenclature and classification 

 been more marked, than in that of the Hydroida. 



Nothing can more plainly exemplify the nature and extent 

 of the changes thus brought about than a comparison of the 

 contents of Mr. Hincks' work with that portion of Dr. John- 

 ston's classical " History of British Zoophytes," the second 

 edition of which dates to no more than twenty years back, 

 which relates to the Hydroida, or, as they are there termed, 

 the Anthozoa hydroida. 



The entire subject of these animals is comprised in 137 

 pages. They are classified in five families and fifteen genera, 

 under which we find enumerated about fifty-five species ; 

 whilst Mr. Hincks has found it impossible to confine his 

 account of the same order to less than a volume of 300 pages, 

 in which he discriminates not less than fifty-seven genera, 

 and no less than 170 species. 



It is obvious, therefore, that such a work was imperatively 

 called for, and it only remains to see how it has been 

 executed. 



To those who are aware of the assiduous attention that 

 Mr. Hincks, in the midst of other important labours, has for 

 many years past paid to the subject, and are acquainted 

 with his numerous contributions upon it in various periodi- 

 cals, it is needless to remark that there is no one among 

 British naturalists better fitted for the task he has under- 

 taken. And to those who upon the appearance* of his book 

 may, for the first time, be induced to direct their attention to 



