REVIEWS. 



A Monograph of the Gymnoblastic or Tubularian 

 Hydroids. Part I. By Geo. J. Allman, M.D., F.R.S.E. 



Although, generally speaking, it is better to await the com- 

 pletion of a work before it is reviewed, it is impossible, in 

 the present instance, not to welcome the appearance, though 

 only in part, of Professor AUman's long and anxiously looked 

 for Monograph on the Hydroida. In one sense, moreover, 

 the present part of the monograph may be regarded as an 

 independent work, seeing that it is entirely devoted to the 

 consideration of the life history of the Hydroida, or their 

 " general morphological or physiological relations as a great 

 natural group," whilst the second part will be devoted more 

 especially to the consideration of the Tubularinae, including a 

 description in detail of all the genera and species of which 

 that subdivision is composed. 



The entire monograph therefore will embrace " a purely 

 descriptive " zoology of the Tubularinas, combined with a 

 careful study of their structure and physiology, and of the 

 structure and physiology of the entire order of the Hydroida," 

 without which it is obvious that the meaning of many 

 things in the economy of the Tubularinse would have been left 

 very obscure. 



Treated in this way, the life history of almost any natui-al 

 group of animals may be made in the highest degree con- 

 ducive to the advancement of philosophical zoology and 

 physiology, for, as is well remarked by the authoi', " when 

 thus investigated, it will be found that the study of the 

 Hydroida possesses an interest far beyond what one may at first 

 be inclined to attribute to beings so simple in their structure, 

 and so apparently insignificant in the place allotted to them 

 in the economy of nature, for we shall then learn that some 

 of the most important facts in morphology and some of the 

 highest laws in physiology find in them their expression and 

 elucidation." 



The term Hydroida, as employed by Professor Allman, 

 includes the Hydrinas, Tahularince, Campamilarince, and 

 Sertularince, which families constitute the hydroida of Dr. G. 



