On tlie structure of Tacnia confusa Ward. 471 



structure is based niainly upoii Observation madu on the headless 

 specimen. 



Exteriial characteristi es. The total leugth of the head- 

 less worin is 8.;") m ; of the other 5.2 m. Reyond the uoticeably long 

 and narrow structure of the proglottids the body does not dilfer niuch 

 in general appearance froni the ordinary forms. The genital pores 

 are rarely very prominent except in the Segments immediately suc- 

 ceeding those sexually mature; as regards the geueral arrangement 

 in the successive proglottids, there is no anomaly, the pores being 

 arranged alternatiug irregularly in the usual manner. The body is of 

 slight structure with much less powerful musculature than T. sagi- 

 nata possesses, and is incased in a very delicate thin cuticula. The 

 extreme length of some of the Segments is the first thing to strike 

 the attention as being un usual and upon measurement it is found 

 that, in the larger worm, at only one point in the chain, just anterior 

 to the sexually mature proglottids, are they wider than long. Ilere 

 they measure on an average about 3 mm wide by 2.1 mm long, this 

 excess of width over length being present throughout about 80 pro- 

 glottids. In the smaller one, the predominance of length over breadth 

 although still considerable, is not so marked, and many proglottids 

 measure somewhat wider than long. The general proportions of this 

 worm may be seen from the second table below. In this case, how- 

 ever, most of the segments that are shorter than broad, show by their 

 slightly wrinkled appearance that they are morc or less contracted 

 lengthwise. 



The following measurements will give some idea of the relative 

 size of ditferent parts of the first worm: 



Posterior proglottids . . 35 mm long by 3.5 to 4 mm wide 



About 1 m further forward 26 „ „ „ 5 „ 



About the middle ... 15 „ „ „ 4.5 „ 



Showing first branchof Uterus 5 „ „ „ 4.5 „ 



Sexually mature .... 4.5 „ „ „ 3.5 „ 



Xear the anterior end . . 1 to 1.2 „ „ „ 0.8 to 1 mm „ 



The smallest present . . 0.9 „ „ „ 0.6 „ 



From the above data it will be seen that the proglottids are 

 broadest somewhat back of the middle of the worm, and that from 

 the smallness of the anterior segments there could not have beeu a 

 very great number with the missiug head. The whole numl)er of pro- 

 glottids present is 762. 



32* 



