SEP 17 19«7 



THE CHJITOGNATHA, OK PKIMITIVE MOLLUSCA. 357 



The Clisetognatha, or Primitive Mollusea. 

 With a Bibliography. 



By 



R. T. oVinther, F.L.S., F.R.G.S., 

 Eellow of Magdalen College, Oxford. 



With 10 Text-tiffures. 



It is the purpose of the present paper to demonstrate that, 

 so far as our present knowledge of the Chastoguatha goes, 

 more numerous and more cogent reasons can be given for 

 allying them with the Mollusea than with any other group. 

 We shall endeavour to show that no organ of importance 

 has been described in Chaetognath anatomy which is not 

 closely paralleled by similar and, we believe, homologous 

 organs among the Mollusea. Indeed, we believe we can go 

 further and demonstrate that the divergences of structure 

 between the Cheetoguathaand the Mollusea are slighter than 

 those known to exist between different orders belonging to 

 the latter phylum. The theory of the Molluscan and Chgeto- 

 gnath affinity explains in a simple manner many facts in the 

 anatomy and developmental history of both groups, while 

 there are no well-established facts which are inconsistent 

 with it. 



Historical Sketch. 



It is not necessary to attempt here a complete review of 

 the stages by which our knowledge of the Chgetognatha has 



VOL. 51, PAKT 3. NEW SERIES. 28 



