8 THE CRAG POLYZOA. 



fertilizing function. No special exit appears in most cases to be provided for the escape 

 of the impregnated ova, or of the embryos, vv^hich it may be presumed are liberated 

 only after the decease or disruption of the parent. 



The above brief exposition will perhaps serve to convey a sufficient general idea of the 

 structure and affinities of, the Polyzoa, but as several important modifications of the 

 typical conformation are found in the various sections of this class, it will be necessary, 

 before going farther, to explain the mode in which the primary divisions are formed. In 

 doing this, I shall follow the arrangement proposed by Professor Allman,^ merely making 

 a few changes in the characters of some of the subdivisions. 



Most of the terms employed for the purpose of this classification have already been 

 explained ; all that is necessary to add is, that by " front" of the cell is meant that aspect 

 upon which the orifice is situated, whilst the "upper or superior" end is that nearest which 

 it is placed. 



' Op. cit., p. 10. 



