516 Arthur E. Shipley 





quently quoted above, begins bis comparison betweeu Bmchiopoda and 

 Chaetogiiatha witb an enumeration of tbe bistological resemblauces. 

 These bave I believe but a very seeondaiy classificatoiy vaine unless 

 taken in conjuuetion witb otber morpbological resemblances , and tbese 

 are not very striking. Tbe formation of tbe mesoblast is tbe same, but a 

 simìlar formation of tbe middle layer is found in sucb diverse groups 

 as Ecbinodermata, Enteropneusta, Cbordata , and probably also in Pe- 

 ripatus. 



Tbe comparison between tbe tbree divisions of a Sagitta aud tbe 

 tbree divisions of a larvai Bracbiopod does not bold, since as was point- 

 ed out above, tbe larva really consists of four segments. Van Bemmelejt 

 States tbat tbis segmentation is indicated in tbe adult, by tbe gastro- 

 and ileo-parietal bands, wbicb are to be regarded as dissepiments ; 

 but tbis cannot be so, since tbese mesenteries are parallel witb tbe 

 anterio-posterior axes of tbe body and intestine and not transverse to 

 tbem. Tbe comparison between tbe vasa deferentia and tbe segmentai 

 Organs is a just one , but segmentai organs of fundamentally tbe same 

 type are very widely distributed tbrougbout tbe animai kingdom. Tbe 

 same arguments apply to tbe dorsal and ventral mesentery , and to tbe 

 nervous system wbicb in botb classes consists of a circum-oesopbageal 

 nerve ring bearing a supra- and sub-oesopbageal ganglion witb two larga 

 nerves springing from tbe latter. 



Finally in Sagitta we find no representatives of tbe lopbophore, 

 sbell, or stalk, wbicb structures are ali eminently cbaracteristic of tbe 

 Bracbiopoda. 



Recently Caldwell bas in a Preliminary Note on Pboronis urged 

 »an entirely new view of tbe bomologies of tbe body surfaces« in Bra- 

 cbiopoda. It is of course impossible to criticize tbis view fully, until 

 tbe complete paper appears : at tbe same time I sbould like to point out 

 tbat tbe facts mentioned above do not warrant tbe Statements tbat 

 »Bracbiopoda are fixed by tbeir ventral surface« and tbat »botb valves of 

 tbe sbell are ventrale Tbese views of tbe body surfaces seem to be 

 founded more upon a comparison instituted between Bracbiopoda and 

 Pboronis, tban upon direct Observation of tbe development of tbe former 

 group . Furtbermore in tbe Bracbiopods tbat I bave examined , I bave 

 found no trace of tbe persistance of tbe prae-oral lobe in tbe form of a 

 epistome. Tbe prae-oral lobe appears to disappear utterly. Finally the 

 internai opening of the segmentai organ lies upon tbe otber side of the 

 lateral mesentery Im in Caldwell's diagram B. 



In couclusion, I would say, tbat I do not consider tbe Bracbiopoda 



