220 THE KELESTOMINJR. [vol. lxxiv, 



universally admitted to be convenient. But an ordinary house 

 does not cease to be a house, even when its windows have been 

 destroyed and its external paint has been lost. In the same way r 

 the term ' zocecium ' seems to be still applicable, even though the 

 soft tissues have disappeared during fossilization. A common 

 procedure, in the study of recent forms, is to remove the soft parts- 

 of the zocecia by means of ' eau de Javelle.' Units thus treated are 

 strictly comparable with the so-called ' cecia ' of fossils, and it was- 

 suggested that it would be very inconvenient to be precluded from 

 describing them as ' zocecia.' 



The Authok, in reply to Dr. Harmer's question concerning the 

 correlation of Cretaceous with Recent cribrimorph Polyzoa, ex- 

 pressed his opinion that there was no direct genetic connexion 

 between them. Any Cretaceous cribrimorph lineage that could be 

 followed to a considerable length, ended in forms so differentiated 

 and so hampered with secondary calcium carbonate that further 

 evolution was inconceivable. Recent cribrimorphs, or ' Cribri- 

 linidse,' probably arose from one or more stocks of membrani- 

 morphs, or ' Membraniporidse,' and were related to Cretaceous 

 forms only by means of ancestors with chitinous skeletons. Even 

 the different Cretaceous cribrimorph families have arisen inde- 

 pendently from different rnembranimorph stocks. 



As to the term ' cecium,' the Author had originally introduced it 

 for the 'shell' of a Polyzoan, as contrasted with the * zocecium, ' 

 which included the shell and the soft tissues in connexion with 

 it. The word, therefore, was established in order to prevent con- 

 fusion of thought and to provide a term comparable with ' conch ' 

 among molluscs, 'tegulum' among brachiopods, and 'theca' among 

 corals — convenient in such compounds as ' protoconch,' ' pro- 

 tegulum, 1 etc. ; indeed, ' protcecium ' has already been used by 

 Cumin gs for the embryonic shell of Polyzoa, and ' ancestrcecium ' 

 by the Author for the shell of the ancestrula or earliest individual 

 (it involves the protcecium as well as the shell of the first colonial 

 individual) in Cheilostome Polyzoa. 



