CuKTis. — Planaria. 
PLATE 19. 
(The figures of this plate are reduced two thirds in the reproduction.) 
Eig. 56. A semi-diagrammatic figure constructed in the same way as figure 
53, of a stage in which the adult condition has been practically 
attained, save that the vasa deferentia do not connect with the penis. 
Zeiss A * X 4. 
Fig. 57-59. Diagrams to represent the development of the atrial cavity from a 
simple cleft to a condition which approximates the adult (figure 34). 
The outline of a sagittal section is drawn in and each figure is from an 
outline with a camera lucida. Zeiss A X 4, 
Fig. 61. The outline of a sagittal section of the region of the mouth and atrium 
of a large specimen in which the atrial organs were degenerating. The 
structures found in a number of serial sections are all shown. At the 
position of the uterus some irregular masses {u), farther back a tangle 
of muscle fibers, a small cavity (c), and a pit on the ventral surface {ap) 
at the position of the atrial pore. These parts are entirely discon¬ 
nected. Zeiss A X 2. 
