114 



from the head are the longest. From these to the end they become grad- 

 ually shorter and wider. In width the segments gradually increase from 

 the head to the end. When first collected the texture of the worms is 

 usually opaque and white, and it is only by allowing them to stand in 

 water that they become transparent enough for study. It can then be 

 seen that each S(»gment is bilaterally symmetrical — that in each half is 

 an independent set of genital organs. These become apparent ata little 

 distance from the head, but show in their best development about half 

 the entire length from the head. From this point on the segments be- 

 come more and more opaque to the end. The genital organs first appear 

 as a little horizontal line on each side ; gradually a little rosette grows at 

 the end of each line; these disappear and the segment becomes filled 

 with the young eggs or embryos, which form the opaque mass. The ex- 

 ternal genitals consist of a round pore on either side of each segment, in 

 which is a minute dot, the opening of the vagina, and an exserted in- 

 tromittent organ. The apparatus is called hermaphroditic, i. e., each 

 half of the segment is capable of fertilizing itself; but it is likely that 

 cross fertilization also occurs. Fertilizatiou occurs about where the 

 dots which line each side of the worm appear plainest. From this 

 point on the eggs are developed into embryos until the end of the worm 

 is reached, when the segments are prepared to retain vitality as indi- 

 viduals for some time after being ejected with excreta to the ground or 

 water. 



Besides the reproductive apparatus there are two so-called excretory 

 canals, one on each side of the worm, running the entire length. I 

 have not observed cross-canals, such as occur in the armed twniw, as in 

 T. marginata. 



There is no alimentary canal. The nervous system is very rudiment- 

 ary, consisting of little more than bundles of nerve fibers. The suck- 

 ers are each supplied with their special fibers, connected together, and 

 each segment is supplied by two long nerve bundles which run parallel 

 to the excretory vessels on either side. Absorption of nutrient material 

 or feeding takes place through the surface of the segments. 



The young e^gs or embryos are polyhedral by pressure, and measure 

 about 0.05 to 0.07™'" in diameter. They have usually two envelopes, 

 between which a considerable amount of oily material is held. They 

 may have three such. Around the embryo is a pear shaped apparatus 

 whose small end is surmounted by a cap with shredded periphery. The 

 embryo Itself is contained in a cavity in the large end of the pyriform 

 covering, and when alive can be seen moving around in it. The em- 

 bryo seems to be a highly refrangeut mass of protoplasm provided with 

 six hooks, and does not look essentially different from the embryos of 

 other tape-worms. The cap with shredded edges is the remnant of a 

 mass which originally included and covered the embryo and its balloon- 

 like expansion. No attempt has been made by the writer to work out 

 its earlier embryology. 



