382 
A Tri-RacUate Tapeworm 
plexus, two of them (c, e) converging to run side by side between two 
suckers (s4, s5) through the posterior third of the scolex (Fig. 2), the 
third (a) running by the side of another sucker (s2). In this part of 
the scolex three vessels appear suddenly to arise de novo. It is possible 
that they are formed by the collection through devious courses of the 
capillaries of the three ventral vessels which disappeared but this it 
has been found impossible to ascertain. They occupy approximately 
the three positions which the three vanished vessels would have 
occupied had they continued their courses. The new vessel between the 
suckers s5, s6 crosses internally to sucker s6, and between suckers s-6 
and si divides into two (g, h), each branch formed being in a similar 
Fig. 2. Transverse section through posterior end of scolex. For explanation 
of lettering see text. 
position to the two just mentioned (c, e). A further branch com¬ 
municates with the new vessel appearing between suckers s2 and s3. 
This new vessel similarly crosses sucker s3, but, instead of dividing 
into two, runs anteriorly, the other vessel of the pair being formed by 
the dorsal vessel (a) previously mentioned. At the posterior two-thirds 
of the scolex a section has the appearance shown in Fig. 2. The excre¬ 
tory system then consists essentially of six vessels (a, d"', c, e, g, h) 
arranged in three pairs, each pair running side by side between two 
suckers, slightly to one side of the main excretory course in the neck. 
Of these six, three (a, c, e) are continuations of the dorsal vessels, the 
other three (d" r , g, h) probable continuations of the ventral. 
4 
