On the reproductive system of Planaria simplissima. 449 



testis iu almost every space between the lobes of the gut and aver- 

 aging 14 on either side, the smallest number I have found any record 

 of. In Planaria simplissima in average taken from 15 specimens in which 

 they were counted gave 9 for the entire number. The total on 

 the right side of the 15 specimens was found, when averaged, to come 

 within a fraction of a similar average for the left side and my count 

 would therefore represent 4^/2 on either side. 



There is a wide degree of individual variation in the entire number, 

 the number on a side and their distance from each other. In the 

 specimens counted the entire number ranged from 4 to 12, the number 

 on a side from 1 to 6, Although the distance between the follicles 

 is irregular they occur within a well defined area. The most anterior 

 is near the ovary, sometimes a short distance in front, more often 

 just outside or above,, the most posterior usually near the free end 

 of the pharynx. They are always dorsal to the gut lobes and lie 

 above or just outside the hue of either vas deferens. PI. 31, Fig. 8 

 shows as much regularity as is usually met with in their distance 

 from each other, while PL 31, Fig. 1, is more nearly representative 

 of the typical irregularity. Both the figures will show the area over 

 which the follicles are distributed. A pairing of follicles on opposite 

 sides of the animal exists only at the anterior end where the head 

 testes of a side and sometimes the one following has a corresponding 

 follicle at about the same point on the other side (PI. 31, Fig. 1 ie l 

 and te 2). From the foregoing it is evident that the only regular 

 arrangement of the testes is in their position dorsally between the 

 gut lobes and in their restriction to a limited area immediately over 

 the line of each vas deferens. In a form with a larger number of 

 follicles closely packed together this would be all one might expect, 

 but with the small number and their distance apart such that no 

 crowding is possible, more regularity should be apparent if there is 

 any metameric arrangement in this form. The fact that the head 

 testes are paired does not seem to be an indication of metamerism, 

 but rather to fulfill the condition of bilateral symmetry, which would 

 make the germinal elements extend about the same distance forward 

 on either side. 



While the connection of the testes with the vasa deferentia is some- 

 what like the condition given by Chichkoff ('92, p. 520) for Planaria 

 montana and presents the same general arrangement as other Planaria, 

 it is almost diagrammatically shown in Planaria simplissima because of the 

 small number of the follicles and their isolated position. Each seminal 



