344 ROXIE A. WEBER. 



is the same in kind and extent as in the group already described 

 except for the digestive tract. In every one of the four there is 

 distinguishable a separate alimentary tract for each member 

 beginning with the mouths. These structures lie very near the 

 nerve cord and are bounded on the inner side by a mass of muscles 

 similar to those which usually lie on either side of the elongated 

 fused pharynx. 



The fixation of the blood vessels was such that they could not 

 be studied. 



The members of these groups to which belong half the speci- 

 mens studied, have undoubtedly been fused along the dorsal 

 side. The relative positions of setse, nephridae, and nerve cord 

 are positive proof thereof. Vedjovsky gives a number of figures, 

 very similar to Figs. 3 and 4, in his paper but he explains the 

 union as being along the ventral side. It is impossible to dis- 

 prove this conclusion for the two members were joined along 

 their entire lengths. In the cases described in this paper, the 

 union was never through more than five segments If, then, the 

 coalescence had been other than dorsal, it is very probable that 

 the nerve cord together with the setae and excretory organs 

 would have swung around to their natural position in the separ- 

 ated portions of the two individuals. This, however, is not the 

 case. Therefore, the conclusion must be drawn that at least in 

 these instances the union is no other than dorsal. 



It is very probable that the one case described by Vedjovsky 

 is also one of dorsal instead of ventral union, and that the cerebral 

 ganglia are composed of half from each member instead of this 

 being the case for the ventral cords, as that author supposes. If 

 those individuals in which the digestive tract was separate had 

 not been found it would not be possible to make this statement 

 for it might be argued that each side of the pharynx was formed 

 from the alimentary tract of one member. But since those 

 cases have been found it can be easily seen that a joining of these 

 structures would have resulted in forming a greatly elongated 

 organ similar to that shown in Vedjovsky 's figures. Further- 

 more, if the union in these forms had been ventral, the pharynges 

 would certainly not have been found in the positions in which 

 they lie, but would have been much nearer together in the central 

 portion and side by side instead of end to end. 



