S. Yoshida 
573 
5. Acanthobothrium ijimai n.sp. 
(PI. XXIII, figs. 12—13 and Text-figure 1.) 
This cestode was collected by Prof. Dr Ijima from the spiral valve 
of Dasyatis akaei (Muller and Henle) in Tokyo, in Feb. 1886. Only 
three specimens were well preserved in alcohol. 
External characters. The specimens are all of nearly equal 
length, about 40 mm. The head (PI. XXIII, fig. 13) is provided with 
four bothridia arranged diagonally and directed forward, reminding one 
of a four-leaved clover viewed frontally; the bothridia are sessile and 
closely united together for some distance as shown in the figure cited, 
each bothridium is ovoid in shape, measuring 1-6—1-7 x 1-2—1-4 mm. 
The sucking surface of the bothridium is divided into three unequal 
loculi by two transverse septa, the anterior loculus is the largest and the 
posterior the smallest; the bothridial border is entire and fairly thick, 
the septa well developed. 
Anterior to the anterior loculus the bothridium is provided with 
one pair of bifurcated hooks, which look like the letter (r) under a 
low magnification. The hook is very small, measuring 0-09—O-ll mm. 
in total length. There are three accessory suckers one large (0-1 mm.), 
and two small (ca. 0-05 mm.) situated in the anterior pad of each 
bothridium, and disposed as shown in the figures; two smaller accessory 
suckers, not readily visible, can only be detected by careful examination. 
The neck varies in length between 0’2 and 0-6 mm. according to the 
degree of contraction; it forms the narrowest part of the body. 
Posteriorly the segments gradually increase in length and breadth, 
the maximum breadth being reached near the posterior end whilst 
they taper posteriorly further back. Segments of maximum size 
measure 0-4—0-6 x !•!—1-5 mm.; their length is greatest in the last 
segments or segment; here they are longer than broad in one specimen, 
and slightly broader than long in two others. The genital pores are 
lateral and irregularly alternate. 
Genital organs. All three specimens are immature and the 
genital organs have not as yet been fully developed except the testes. 
The testes are spherical or oval in shape and scattered throughout the 
medullary field excepting the space occupied by the female organs. 
Most of the vas deferens is in the progressive stage of development, 
its distal part with the cirrus pouch has not yet become differentiated 
from the cellular mass of the Anlage, which shows a longitudinal central 
