284 A. T. MASTERMAN. 



geuetic connection appears to be the only conclusion. Never- 

 theless, for reasons stated below, I would suggest that 

 Phoronis be considered as constituting a distinct subdivision 

 of the Chordata, for which the name Diplochorda is 

 proposed. 



In this group the leading anatomical characters of the highest 

 Chordata have their rudimentary homologues, and the dis- 

 tinctive features of the Vertebrata are reduced to so general 

 a type that the transition to the true In vertebrata is but a 

 small step. 



Whatever value this research may have as an addition to 

 our knowledge cannot therefore be summed up by the looked- 

 for result that the Chordate affinities of Phoronis will be 

 definitely acknowledged, but will lie in the fact that the 

 recognition of this relationship will bring the base of the 

 Chordate tree into contact with certain Invertebrata which 

 have always been more or less connected with Phoronis. 

 My suggestion of the group Archicoelomata is merely the 

 embodiment of this conception, and the apology for its creation 

 will be forthcoming if it may lead specialists in the groups of 

 Sipunculids, Polyzoa, Brachiopoda, and Echinoder- 

 mata (our great sedentary groups) to hold in view the possible 

 occurrence of pre-chordal characters in the ontogeny of their 

 investigated types. The discovery of the close connection of 

 the Tunicata with Amphioxus served rather to remove 

 them from their former alliance, and cannot be said to 

 have pointed to any link between the Chordata and the 

 Invertebrata. 



The removal of Balanoglossus, and later the association 

 with it of Cephalodiscus and Rhabdopleura, allowed the 

 Chordate ancestry to be traced back to pre-chordal (Lankester) 

 times ; and the study of Phoronis, and especially its develop- 

 ment, takes us back to the definite meeting-place between the 

 two great types of segmented animals, the segmented In- 

 vertebrates and the higher Chordata. 



During the progress of this work a detailed comparison 

 was made between the several organs of Phoronis and Acti- 



