8 



BULLETIN 9C, UNITED STATES NATIONAL MUSEUM. 



therefore in the study of the morphological variations of the organs 

 we now substitute that of their physiologic functions. Our studies 

 are therefore always directed toward the discovery of functions 

 which modify the skeletal form. 



Family. — All the species which have the same larval form have 

 the same lineage and belong necessarily to the same family; there- 

 fore the family is characterized by the larval system. The ovicell 

 in which the larva developes is necessarily in rapport with it, and 

 a Ivnowledge of its structure gives the essential characters for readily 

 interpreting the j)hysiological purpose of the morphological and 

 skeletal variations. 



Genus. — A really natural genus differs from another genus only 

 in possessing a different function and in the different form of any 

 skeletal part. The essential functions common to all bryozoa with- 

 out exception are: 



1. Passage of eggs and escape of the larvae (=rapport of the 

 operculum and the ovicell). 



2. Hydrostatic system and extrusion of the polypide (=:form of 

 the aperture and rapport of the operculum with the compensatrix). 



3. Calcification and chitinization (=nature of the skeleton and 

 of the frontal considered as immediate deposits of the endocyst). 



We have rigorously followed this principle in the establishment 

 of our new genera and we have also modified the diagnoses of the 

 described natural genera which were often incomplete. 



The function of the avicularia and of the onychocellaria is not 

 known but it can not be common to all bryozoa because many species 

 are deprived of these structures; these structures therefore can not 

 furnish good generic characters. Nevertheless there are some groups 

 in which their presence appears to be absolutely indispensable to the 

 life of the zoarium and we have therefore considered them sometimes 

 in our generic diagnoses. 



The general classification of the Bryozoa showing the larger sub- 

 divisions of the Cheilostomata is printed below for convenience of 

 reference. 



Class. Subclass. Order. Suborder. Division. 



fCtenostomata. 



Cyclostoinata. 



Trepostomata. 



Gymnolaomata. J Cryptostoinata. 



Bryozoa. [Malaco.stejra. 



(Anasca. J Coilostega. 

 [Pseiulostef^a. 

 Ascopliora. 

 Phylactolaeruata. 



