280 
Taenia crassicollis 
The length and the width of segments in various parts of the worm 
are given in the following table : 
Last 
segment 
loth segm. 
from last 
20th „ 
30th „ 
40th „ 
50th „ 
70th „ 
80th „ 
90th „ 
lOOth „ 
First 
segment 
Length 
7’0 mm. 
4-0 
3-0 
2-5 
2-0 
2-0 
1-5 
1-0 
0-75 
0-5 
0-1 
Width 
1’5 mm. 
2-3 
2-5 
2-5 
2-5 
2-0 
2-0 
2-0 
2-0 
1'5 
0-6 
The above table shows that the segments successively increase in 
length from the anterior to the posterior end, but the width of 2’0-2'5 mm. 
persists throughout the greater part of the body except for short 
portions at both ends. 
Each wing of the prismatic tape-worm in question is similar in 
all respects, that is, in size, form, length, width of segment, and in 
radiation of the angle of the wings from the axis of prism, so that a 
cross section would have the appearance of a regular tri-radiate star. 
The scolex (PI. XX, fig. 1) measures I'o mm. in width and, instead of 
four, is provided with six suckers grouped into three pairs, each of which 
is situated on the anterior end of each wing. All of the suckers are 
equally prominent and turn forward and outward. 
The hooks are 42 in number, arranged in two crowns, the hooks 
of one circlet alternating with those of the other, as in the ordinary 
T. crassicollis. 
The internal structure does not need a detailed description as it 
agrees in its main characters with that of normal individuals of this 
species. I shall therefore restrict myself to a brief description of the 
excretory system and such of the genital organs as are more or less 
peculiar and different from those of normal specimens. 
In each wing of the tri-radiate worm, the two main longitudinal 
canals of the excretory system lie near the lateral side of the medullary 
portion, just inside the nerves. The two canals, instead of being situated 
dorsally and ventrally and superposed, run side by side, as in the ordinary 
T. crassicollis, and as is often the case in other forms. The outer canal 
is the larger, but the small canal possesses a more muscular wall. It is 
obvious that the former is the ventral, and the latter the dorsal canal, 
both from analogy with other forms and from the connexion of the 
transverse canal with the larger one ; I shall refer later to a peculiar 
mode of this connexion. The ventral canals in the three wings are 
connected with each other by the transverse canals at the posterior end 
of each segment. In cross sections of this region of a segment, we find 
the thx’ee transverse canals radiating into each wing from the axis of the 
prismatic body (PI. XX, fig. 7, tv.). The connexion between the ventral 
