346 ROXIE A. WEBER. 



brains lie on the same side and are connected to the cords by 

 means of commissures, a condition very similar to that found in 

 normal single individuals. The brains however in this instance 

 are joined to each other. In one of the individuals the com- 

 missural connection between brain and cord can be seen beyond 

 the point of separation, but in the other member the two ganglia 

 of the brain seem to be separated and joined separately to the 

 cerebral ganglia of the first member. 



In No. 93, shown in Fig. 14, there is present only one set of 

 cerebral ganglia greatly elongated. It lies on that side of the 

 pharynx opposite the cords and is joined to that structure in one 

 member by two commissures, to that in the other by only one. 



A study of sections through No. 2 reveals a condition similar 

 to that in No. 90. There are two distinct sets of cerebral 

 ganglia, one joined to each nerve cord as in normal individuals 

 and a connection between the two brains much as between the 

 two cords in No. 70. 



4. That group of double monsters in which the union between 

 the two individuals has been side to side with both mouth 

 openings on the same side, illustrated by Nos. 67 and I. 



In No. i the union is through one segment only as indicated 

 in Fig. 16, Plate III. There is a single mouth opening lined 

 with the columnar epithelial cells, from which the digestive 

 tract of each individual passes inward. There can be seen on 

 one side of the pharynx in a transverse section a single set of 

 cerebral ganglia which is joined to the ventral cords by commis- 

 sural strands extending over the pharynx. There are no such 

 structures to be found on the under side of the alimentary tract. 

 On the opposite side of the section there can be traced a con- 

 nection between the cords themselves. Fig. 17, Plate III., is a 

 section through the united portion of No. I showing the single 

 pharynx, cerebral and ventral ganglia and a portion of the 

 strand of nerve tissue connecting the two cords. 



A study of sections through No. 67, shown in Fig. 18, Plate 

 III., will show that the two mouth openings have been joined 

 into one, and that the ventral cords lie on one side of the com- 

 mon pharynx and the cerebral ganglia on the other. There is 

 only one set of brain ganglia to be found in this monster, but, 



