No. 7.—THE LIFE HISTORY, THE NORMAL FISSION, 
AND THE REPRODUCTIVE ORGANS OF 
PLANARIA MACULATA. 
BY WINTERTON C. CURTIS. 
Introduction. 
The work of this paper has been carried on at the Johns Hopkins 
University during the three years previous to 1901, and I wish to 
express my sincere gratitude to Prof. W. K. Brooks for his kindly 
help and guidance throughout the course of my study. I am also 
indebted to the authorities at the Marine biological laboratory, 
Woods Holl, Massachusetts, for the privileges extended to me 
by that institution in the course of my work there during the 
past three summers. 
The absence of reproductive organs during the entire year in 
Planaria macidata from certain localities and the appearance of 
these organs regularl}^ each year in specimens from other localities, 
aroused my interest and led me to seek some explanation. While 
accumulating data upon the presence or absence of these organs in 
different localities and seasons, I found in the localities where repro¬ 
ductive organs are not developed abundant material for a study of 
the normal fission, and since the normal fission of planarians, while 
mentioned by many writers during the past ten years, has not been 
adequately described or figured in a single instance, with the possi¬ 
ble exception of Planaria Jissipara. (Kennel, ’88) which presents 
just the opposite of the type of fission in Planaria macidata^ I have 
attempted a thorough description of this process as it occurs in the 
latter species. The entire absence of reproductive organs in many 
localities remains considerable of a mystery, but I give the data 
thus far obtained under the head of life history. Finding that the 
reproductive organs of this common form had never been described, 
I published, in 1900, a short note on their anatomy and develop-, 
ment, and these observations are further elaborated in this paper. 
