550 PKOCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
ends with the remains of an old ovary, must of course develop all 
their organs anew in the fall. This development of the reproductive 
organs in small worms collected from sexual localities in the early 
fall is what I described in a preliminary paper last year and will 
here follow through more in detail. 
The Development of the Reproductive Organs in 
Small Worms. 
Lang’s statement (’81) that the sex cells of planarians arise from 
the epithelium of the gut has, so far as I know, never been con¬ 
firmed, and I think we may set it down as an error in the interpre¬ 
tation of his data. Beyond this and the mere statements that the 
testes are at first solid and that the oviduct begins as a solid rod of 
cells, he says nothing of the development. 
The description of the development given by Ijima (’84) seems 
to be correct as far as it goes, and he indicated the essential parts of 
the i^rocess quite correctly. He says that the development of the 
atrium and the penis is like a repetition of the process by which the 
pharyngeal pocket and pharynx are formed, since it begins as a cleft 
among a mass of mesoderm cells from the anterior wall of which 
cleft the penis grows out. Ijima also described the sex cell and the 
yolk glands as developing in situ from individual cells of the 
mesoderm. 
Woodworth (’91) describes the yolk glands of JPhagocata gracilis 
as originating by outgrowths from the parovarial masses found in 
that species and disputes Ijima’s description of their origin in situ. 
Chichkoff (’92) inclines to Woodworth’s view although wdth no 
observations of his own. 
Since none of the foregoing works offers a complete description 
of the development of the sexual organs, I submit the description of 
this process as follows. I must preface this account by saying that 
I do not know whether the stages I am describing are from egg- 
embryo worms or from worms which have been reduced to a small 
size by a period of asexual multiplication. A reference to the sec¬ 
tion at the beginning of this paper upon the life history of 
Planaria maculata in different localities will explain this state¬ 
ment. In the locality numbered 1 (page 517) it will be seen that 
after the eggs are laid, the reproductive organs disappear and the 
