352 REPORT— 1863. 
and I have endeavoured to embody in the following Report the results of this 
study, so far as they regard reproduction, combining them with what has been 
added by the labours of others in the same field, so as to present, as far as 
possible, a comprehensive survey of this department of research. 
Among the older observers, those to whom, during the last century, we 
are chiefly indebted for advancing our knowledge, both morphologically and 
physiologically, of the Hyprorpa, the names of Ellis and Cavolini stand con- 
spicuous; while, during the present century, the labours of Sars, Ehrenberg, 
Lovén, Krohn, Kolliker, Gegenbaur, Steenstrup, Van Beneden, Dujardin, 
Leuckart, Fritz Miller, Claparéde, and others on the Continent, Agassiz, 
Clark, and M°Crady in America, and in our own country those of Dalyell, 
Huxley, Alder, Hincks, Busk, Strethill Wright, and Greene, have thrown 
new and important light upon their structure and functions, and have led to 
the determination of the true import of many phenomena which would other- 
wise have remained imperfectly understood. 
Among the works which have of late years done most in the simple de- 
scriptive zoology of the Hyproma must be mentioned the ‘ Monograph of the 
British Naked-eyed Meduse,’ by Edward Forbes, and the ‘ History of the 
British Zoophytes,’ by George Johnstou—works whose specific determination 
of the British forms have greatly smoothed the way towards their profounder 
study, affording to the anatomical worker of the present day the same kind 
of aid which the zoological descriptions in Ellis’s classical ‘ Essay on the 
Natural History of Corallines’ gave to the earlier investigators. 
In combining anatomical with zoographical description, the 4th volume of 
the great work of Agassiz (Contributions to the Natural History of the 
United States of America, 1862) holds a preeminent place in the fulness of 
its descriptions and the profuseness and excellence of its illustrations; and 
though I shall have occasion, in the following pages, to dissent from some of 
the views of the celebrated American zoologist, I must here express my ad- 
miration of this fine contribution to the zoological literature of our day. 
Besides the advantages I have derived from consulting the works of the 
various authors named above, I must express my thanks for much valuable 
information derived from personal correspondence with numerous friends, 
especially Professors Huxley and Greene, the Rev. Thomas Hincks, Mr. 
Alder, and Mr. Busk. 
Some apology may be deemed necessary for the number of new terms in- 
troduced into the following pages; I do not believe, however, that I have 
employed one which could be advantageously dispensed with. Among the 
means which have tended most to advance a philosophic zoology is a well- 
selected and accurately defined terminology ; while few things have tended 
to retard it so much as ill-selected and loosely applied terms. A rigidly de- 
fined and significant terminology not only facilitates in a way which it alone 
can do the communication of scientific ideas, which would otherwise have to 
be expressed by cumbrous circumlocution and phrases which fail to impart 
definite ideas, but, like the symbols in algebra, it even becomes a direct instru- 
ment in the investigation of truth. 
The subclass Hyprorpa of the following Report includes the orders Hydrida, 
Tubularida, Campanularida, and Sertularida, being so far exactly coextensive 
with the Hydroida of Johnston. It necessarily embraces, however, most of 
the so-called naked-eyed Meduse ; for a large proportion of these are now 
known to be the free zooids of polypoid forms belonging to the Tubularida and 
Campanularida, while those which have not yet been so traced—provided we 
have no reason to regard them as the free zooids of the SrenonopHora—and 
