282 A. T. MASTERMAN. 



that of biology, have always been the keys with which to unlock 

 the secrets of the natural system. 



Amongst these types the genus Phoronis holds pre- 

 eminently the position here referred to; for though its first 

 discovery only dates back some forty years, or, including its 

 extraordinary larval form, a little over fifty years, and the 

 genus only comprises some half-dozen known species, yet a 

 long series of investigators have devoted their energies at one 

 time and another upon it, and the divergence of opinion re- 

 sulting from this and the attempt to point out its affinities 

 has been truly remarkable. 



The larval form, Actinotrocha, first discovered by Miiller 

 in the North Sea, was conjecturally assigned by sundry 

 zoologists to the Turbellaria, Rotatoria, Polyzoa, Mol- 

 lusca, Sipunculoidea, Annelida, and so on; and since 

 its transformation into the adult Phoronis was proved it 

 has been variously enligned with the Polyzoa, Sipuncu- 

 loidea (Gephyrea), Chsetopoda, Brachiopoda, and so on. 



The whole history and literature of the Phoronidea have 

 been so exhaustively dealt with, firstly by Professor Mcintosh 

 (15), and secondly, so recently as 1892, by Dr. Cori (7), that it 

 is scarcely justifiable to repeat the account here, especially as 

 the memoir by Dr. Cori is the latest publication till within 

 the last year dealing with the genus. Suffice it to say that 

 the generally accepted opinions of zoologists appear to be 

 either in favour of regarding Phoronis as an aberrant 

 Sipunculid^ or as an aberrant Polyzoan.^ An intermediate 

 position between these two groups, or between one of them 

 and some other distinct groups, such as Mollusca or Bra- 

 chiopoda, has also been held by many.^ 



It was thus felt that the last word had not been said upon 

 Phoronis, and that a renewed investigation of the group, 

 especially with the assistance of modern methods, might be 

 attended by profitable results. 



1 Krohn, Schneider, Wilson, MetschnikofP. 



2 Ostroumoff, Barrois, Gegenbaur, Mcintosh, Lankester, Cori. 

 ^ Kowalevski, Claparede, Caldwell. 



