CURTIS: LIFE HISTORY OF PLANARIA MACULATA. 549 
table shows the reduction of the atrium to a mere collection of 
nuclei, the disappearance of the oviducts, and the reduction of the 
ovaries to insignificant masses containing only a few ova (pi. 17, 
fig. 50). The collection of nuclei at the position of the atrium has 
the appearance of forty or fifty small parenchyma nuclei such as are 
shown in figures 42 (plate 15) and 43 (plate 16) at np^ which sur¬ 
round, and are imbedded in the edges of a small area that takes a 
good deal of any plasma stain and is more dense than the cytoplasm 
of the surrounding parenchyma. The normal fission begins at 
stages of degeneration when the old ovaries and oviducts and some 
trace of the atrium still remain (specimen 3 in the table), and since 
the plane of fission is just in the region of the disappeailng atrium, 
some cases in which the atrium had entirely disappeared much 
sooner than in others, may be attributed to the early occurrence of 
the fission. 
The table traces the stages of degeneration down to a condition 
where very small rudiments of the ovaries remain and sometimes 
some nuclei to mark the old atrium. There can be no mistaking an 
old ovary (pi. 17, fig. 50) for one just developing (pi. 17, fig. 49), 
although the number and size of the ova maj^ be about the same in 
a single section, and this condition is hardly questionable as the last 
stage in the degeneration of the sexual organs. The normal fission, 
which sets in about this time, by cutting off tail pieces makes many 
good sized worms which have no sign of the old organs, and the 
young of the same year have increased in size to such an extent 
that they can be no longer distinguished from the worms resulting 
from the fission of the adults. Specimen 6 shows, however, that 
the production of the new reproductive organs, as fall approaches, 
does to a certain extent overlap the degeneration of the old. In 
such cases, while portions of the old organs still remain, there are 
cords of cells appearing in the parenchyma above either nerve cord 
which later give rise to the testes. Such a cord is shown in plate 
16, figure 46. The origin and later history of these cords and 
masses of cells will be taken up under the development of the 
organs in small worms. Whether the old ovary in original head 
ends in which it exists, ever develops into the new one, I cannot tell, 
as the original head pieces are of course like all the other worms 
externally and none of the specimens sectioned showed anything to 
give a clue. The majority of the individuals not being original head 
