A STUDY OF METAMERISM. 413 



metameres. The openings of the vasa deferentia were not 

 seen on the outside, but dissection showed the ovaries to be 

 present in the 13th metamere. 



Conclusion. — In these three cases where the spiral in- 

 volves the 15th metamere the reproductive organs appear in 

 their normal half-metameres. In all of these cases the false 

 union of metameres that produces the spiral is above. The 

 lower surfaces of the half-metameres join one another as under 

 normal condition, — that is, the 14th below and on the right 

 side joins the 14th, &c. On the dorsal side the reverse is 

 true, — that is, the 14th joins the I5th half-metamere, &c. As 

 the reproductive organs are in the lower part of the segment, 

 we would expect to find them still in their normal segment 

 (and not in any way modified), and this we do find in all cases 

 recorded. 



2nd Case. — In fig. 29, a,b,c, a spiral is drawn involving the 

 14th, 15th, and 16th metameres. The spiral begins in the 

 14th half compound metamere (14 — ^). The openings of the 

 vasa deferentia are present in their normal half-metameres. 



In fig. 30, A, B, c, a spiral involves the 15th, 16th, and 17th 

 metameres. Here, as in the last case, the openings of the vasa 

 deferentia are not afl'ected. 



In fig. 31, A, B, a similar spiral involves the 15th, 16th, 17th, 

 and 18th metameres. Here a half compound metamere 

 (15 — y¥), beginning the spiral, carries the openings of the vasa 

 deferentia on their normal 15th metamere. 



In fig. 32, A, B, a spiral involves the 15th, 16th, and 17th 

 metameres. The openings of the vasa deferentia occur on 

 their normal metamere, which forms the anterior limb of the 

 half compound metamere (15 — yf) that begins the spiral. 



Conclusion. — In none of these last cases does the presence 

 of a half compound metamere involving the 15th metamere 

 affect the openings of the vasa deferentia. 



General Conclusion from Category D. — Nearly every 

 case points unmistakably to the conclusion that, however 

 falsely the segments may unite in front of the 15th metamere, 

 or so that the 15th metamere is involved in a spiral or half 



