IXTRODrCTIOX. 
XXV 
adnate growth being of generic value. Thus, to quote an instance 
from such primitive organisms as the Foraminifera, the essential 
difference between Brady’s two genera, Rhizammina and Sagenella 
(altered to Sagenina by Chapman^ owing to the prior use of 
Sagenella among Bryozoa), is that Rhizammina is free and Sagenina 
attached. There are Foraminifera in which the shell is either 
free or attached, as they may grow either on a shell or resting 
loosely on the sea-floor; and no doubt many zoological classes 
include some members that have a free mode of life and others that 
are attached ; but the consequent differences have led to their being 
usually assigned to different genera and often to different families. 
So great a difference in habit in such comparatively highty organized 
animals as the Bryozoa seems to be a natural generic distinction ; 
but it also has the recommendation of convenience, for the same 
specific names have been used in different genera, and a merging of 
genera would necessitate confusing changes in the names of the 
species. 
I am, therefore, glad that the ‘retrograde’ step of the recognition 
of Berenicea has been taken by most recent writers on the Cyclo- 
stomata ; for if such genera be abandoned, the nomenclature of 
the Cyclostomata concerned will he hopelessly confused. 
Differences of opinion as to the value of some characters only 
affect names, but the Cyclostomata are also troubled with 
differences as to the fundamental principles of classification. 
The Order Cyclostomata was founded by Busk in 1852,^ but 
the first important classification based on adequate representation 
was that by d’Orbigny.^ His classification included most of the 
then known Bryozoa. His work, prepared after many years’ study 
of recent and fossil Bryozoa and based on a very large collection 
of both, is probably the most important single work in the whole 
literature of Bryozoa. It was issued in parts from 1851 to 1854, 
but many of d’Orbigny’s new genera were known from preliminary 
diagnoses in 1849.^ 
The classification adopted by d’Orbigny was greatly modified 
* F. Chapman. The Foraminifera, 1902, p. 127. 
2 G. Busk. In Voyage H.M.S. “ Rattlesnake,” vol. i., App. p. 346. 
2 A. d’Orhigny. Paleont. frau 9 aise, Terr, cretaces. Bryozoaires. 
* A. d’Orbigny. Prodrome de Paleontologie, etc. 
