NOTES AND COMMENTS [march 



Systematic Position of Phoronidea. 



Professor L. Eoule has published a short paper {Gomjptes rendvs ae. 

 sci, Paris, Oct. 1898) upon the above subject. He has followed the 

 development of Phoronis sabatieri, and has been led to suggest one 

 more possible origin for the Vertebrata. 



He accepts Mr. Masterman's conclusions with regard to the systematic 

 position of Phoronis, in that he considers its nearest affinities to be with 

 the so-called " Bryozoa Pterobranches " (or in other words, C&phalo- 

 discus and Bhabdopleura) and holds that the Chordata may be directly 

 traced through Actinotrocha. He is led to this mainly by accepting 

 the homology of Masterman's so-called " notochords " with the simi- 

 larly-named organ in the Chordata, confirming this author's description of 

 their origin and histological structure. 



On the other hand, he finds in P. sabatieri, that the " notochord " 

 is unpaired and ventral, instead of paired and lateral. In the species 

 investigated by Masterman the pleurochords are strictly lateral, though 

 the fact that the " oesophagus " enters the pharynx at its antero-dorsal 

 corner gives them a position apparently ventral to the pharynx. Dr. 

 Eoule does not furnish any figures, so that one cannot say whether this 

 fact has any bearing upon his conclusions, and in any case the unpaired 

 condition is a remarkable difference in so closely allied a species. 



Still more remarkable is the conclusion to which the author is led 

 by these facts. Actinotrocha has a ventral notochord, the vertebrate has 

 a dorsal one ; what more natural than to turn the former upside 

 down ? 



Professor Eoule reverts to the idea that Actinotrocha is a trocho- 

 phore (in spite of its five coelomic cavities described by Masterman 

 to which he makes no allusion), and hence he speaks of the 

 " notocorde de ces Trochophores," and the old conclusion is eventu- 

 ally reached that " le Vertebre est un Annelide retourne." The author 

 must not, however, be understood to revert to anything so common- 

 place as the now well-known morphological somersault of the annelid 

 aspiring to Chordate structure. The Actinotrocha, already inverted in 

 the pursuit of progress, turns itself horizontally through 180°. Its 

 mouth then becomes the vertebrate neurenteric canal, and its anal 

 extremity becomes moulded into the head of the Vertebrate. Truly 

 there is a divinity that shapes our ends, invert them how we may ' 

 Professor Eoule's theory of vertebrate origin will doubtless compare 

 favourably with the various speculations centering round the king- 

 crabs, spiders, leeches, and worms from which we are invited to trace 

 our lineage. 



