548 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
be seen to represent something quite different from the develop¬ 
mental stages; and when the months of the year at which they 
occur are noted, they cannot signify anything but the stages of 
degeneration. Out of a considerable number of cases I have 
selected six as showing all that is necessary,* and these with the 
month at which they were found are indicated in the first column. 
In the columns following, the presence or absence of the ovaries, 
yolk glands, atrial organs, vasa deferentia, and testes, is indicated 
and peculiar cases are pointed out by some comment. 
The testes by about the tenth of June, although still large, have 
a much smaller number of spermatozoa and fewer mother cells in 
their walls. They seem to become exhausted by the using up of all 
the germ cells so that nothing remains but a cleft in the paren¬ 
chyma which then collapses. Contrary to Chichkoff’s view (’92, p. 
522) that portions of the testes in the forms he studied remain and 
produce the new testes of the next year, I cannot find that in Pla- 
naria maculata any sign of the old testes remains. The disappear¬ 
ance of the testes is therefore the first stage in the degeneration. 
This may be compared with Woodworth’s (’91) mention of what 
occurs in Phagocata gracilis. He says (p. 30), “While the yolk 
glands are still in an early stage of development, spermatogenesis 
has been completed, the testes have disappeared and the sperma¬ 
tozoa are found filling the vasa deferentia”; and again (p. 31), 
“ after the spermatozoa have found their way through the vasa de¬ 
ferentia all traces of the testes disappear.” In Planaria maculata 
the vasa deferentia persist for some time after the disappearance of 
the testes and are to be found reaching almost to the ovaries as in 
specimen 2 of the table. 
The third case in the table is the most important. Testes, 
vasa deferentia, and yolk glands have disappeared. The ovaries 
with their oviducts, which extend back as far as the atrium, remain 
intact, but in the region of the atrium are found only the remains of 
the atrial organs. Figure 61 (plate 19) represents what several 
consecutive longitudinal sections show in this region. There are 
some structureless masses at the position of the uterus (n), a cavity 
(c) at the place where the penis would be normally found, and a 
small pit in the ventral surface («/?) which represents the atrial 
pore, but there is no connection between these portions. The fur¬ 
ther degeneration as illustrated by specimens 4, 5, and 6 of the 
