FIG. 41. Horizontal section through same double monster as in last two figures. 

 The section is at a still deeper level, and passes below the auditory organs, through 

 the basal parts of the brain and the lower segments of the eyes. All four-optic 

 nerves and fissures are seen. Owing to the curvature of the specimen, the body is 

 cut through somewhat obliquely, and shows the two notochords and head-kidneys, 

 as well as the composite spinal cord and the median muscular mass. There is 

 greater apparent duplicity in the forepart of the body than in the posterior cerebral 

 region. For other references see under PI. I. Fig. i. (xi2.) 



FIG. 42. The anterior part of last specimen shown in higher magnification. 

 (xai.) 



PL. XI. 



