448 WINTERTON C. CURTIS, 



reproductive organs, upon which the identification should be based, no 

 part of the internal anatomy differs greatly from what is found in 

 other forms. The gut, muscular systems, etc. conform to the simplest 

 Triclad type, which is to be correlated with the simple structure of 

 the reproductive organs. Testes few, at season observed 4 — 5 on either 

 side, arrangement irregular. Ovaries about V^ of total length from 

 the anterior end, often consisting of disconnected lobes. No secondary 

 sheath about the penis, relation of penis to atrium an exact repetition 

 of pharynx to its atrium. Vagina entering atrium in the upper 

 posterior region. Uterus a straight tube extending forward above the 

 atrium and without terminal enlargement. Short common oviduct 

 passing posteriorly, quickly dividing and curving forward on either 

 side. No accessory glands other than the shell gland of the vagina. 



The Reproductive System. 



It was the purpose of this study to work out the anatomy of 

 the male and female reproductive organs in Planaria simplissima and 

 follow during the winter mouths any changes occurring in the struc- 

 ture or activity of either system preparatory to the reproductive sea- 

 son. As the work progressed some facts were learned regarding the 

 anatomy of other parts. 



I. Anatomy, 



The male system, shown in the general figures (PI. 31, Figs. 1 

 and 8), consists of testes, fine testicular canals, vasa deferentia, seminal 

 vesicles and penis. So far as I have ascertained it does not possess 

 accessory glands at any point. 



The testes are lobed folhcles situated in the dorsal part of the 

 body parenchyma and are in every way like the follicular testes 

 typical for other Triclads. Their position and relative size will be 

 seen in the figures just referred to. The points worth noting are 

 their small number, irregular arrangement and connection with the 

 vasa deferentia. 



They are few in number when compared with other forms. Lang 

 ('81) describes 25 on either side in Gunda segmentata, Ijima ('84) 

 describes them in Planaria polychroa as closely packed together even 

 to the tail, Wood worth ('91) in Phagocafa gracilis as very numerous, 

 and WiiKELER ('94) (îO— 100 on either sid(î in Bdelloura Candida, 

 Sijucoelidium pellucidtmi is figured by the last author as having a 



