A STUDY OV METAMERISM. 405 



There can be no doubt but that au examination of a larger 

 number of worms would show other combinations, but these 

 are sufficient to show that variations in the position of the 

 vasa deferentia do occur. 



c. Two worms in this lot showed a doubling of the openings 

 of the vasa deferentia on one side. 



In fig. 51 we find on the 15th metamere a pair of openings, 

 right and left; but in addition to these we find on the left side 

 of the 16th segment another opening of a vas deferens. 



In fig. 52 we find the 15th metamere with its pair of 

 openings, the right somewhat enlarged. On the left side of 

 the 14th metamere another opening is present, as shown in 

 the figure. 



Dissections were made of nearly all of the worms recorded 

 in categories a, b, c. There is always the possibility of mis- 

 takes when only surface views are examined, but fortunately 

 in all cases recorded the evidence from internal structure has 

 supported the conclusion from the external appearance. More- 

 over additional data of considerable interest has, I think, been 

 gained. 



We may examine first the results of dissections of worms 

 in which the paired openings of the vasa deferentia are on 

 some other segment than the 15th. 



No. 1. Openings of the vasa deferentia on the 10th meta- 

 mere, fig. 53. The ovaries were present two metameres in 

 front of the vasa deferentia openings, i.e. the ovaries were in 

 the 8th metamere. All of the other parts of the reproductive 

 system were present and normally developed. The brain 

 appeared in the 1st metamere. 



No. 3. Openings of the vasa deferentia on the 11th meta- 

 mere. Only one ovary was found in the 9th metamere (left 

 side) ; the other probably lost in the process of dissection. 



No. 3. Openings of the vasa deferentia on the 12th meta- 

 mere. The ovaries were found in the 10th metamere, fig. 54. 

 The first segment seemed incompletely regenerated. 



No. 4. Openings of the vasa deferentia on the 14th 

 metamere, fig. 55. The ovaries in the 12th metamere. 



