140 DR, J. STEPHENSON ON THE MORPHOLOGY, CLASSIFICATION, 



Since, therefore, the criteria for estimating the numbering of 

 the segments in the anterior part of the body of Destnogaster 

 allow of results of only doubtful value, I believe we are justified 

 in taking a numbering which corresponds — allowing for the 

 evolution described above — with that of the other genera of the 

 family. In any case, if subsequent investigations, directed 

 specially tovvards this point, should show that the accepted 

 numbering is correct, I should, prefer to account for it by 

 assuming an increase in the number of segments in the anterior 

 part of Desmogaster after the stocks of Ewpolygaster and Draioida 

 had been given off, rather than by an independently produced 

 elimination of a segment, or a dislocation forwards of all the 

 organs, in these two genera. 



The following figures show the relations of the three genera ; 



Text-figure 14. 



Vii s Ulll 



a 



XII 



'± 



D 



A. Desmogaster ; 13. JSupoli/gaster ; C. Drawida and MoiiUigaster. 

 The actual segaieiits are numbered, and the relations indicated. 



