NEW ASEXUAL TAPEWORM. 831 



be really composed of two segments, if we consider the condition 

 of the water vascular system therein. The two main longitudinal 

 vessels of this system extend well forwards into this compound 

 segment, and the outer ventral vessels are connected by two 

 transverse vessels, thus indicating, as I suggest, the double 

 nature of this apparently single segment. Towards the centre 

 of the specialised anterior segment is a large group of deeply- 

 pigmented oval bodies, which appear to be special pigment-cells. 

 They are as large, or nearly so, as the calcareous corpuscles which 

 are very abundant in this worm. In the middle of the concave 

 anterior border of these two fused segments is quite a small 

 conical projection, than which nothing else at all comparable to 

 a scolex exists. There is no sign of any breakage at the summit 

 of this which might suggest that a scolex had been accidentally 

 detached. 



It is a somewhat remarkable fact that these conditions (or, at 

 any rate, something very near to them) occur in the genus 

 Dioicocestus ; for, as will be pointed out later, the genus with 

 which I am concerned in the present paper shows some likeness 

 to the Acoleidse and even to the genus Dioicocestus, which is of 

 that family. In Dioicocestits acotylus, Fuhrmann * has described 

 and figured the practical absence of suckers and the very rudi- 

 mentary condition of the rostellum— a state of affairs which is 

 not found in the other species of this genus. The figure referred 

 to also shows — as I have described in my species — the absence 

 of any marked diminution in calibre of the body at the head end. 

 But it must be remembered that the Dioicocestus was a fuUy- 

 developed sexual worm. 



§ Structure of the Buds. 



It now remains to consider the minute anatomy of these out- 

 growths and their nature. As to the latter query, there are, as 

 it appears to me, only two alternatives. These outgrowths must 

 be either " tentacles " of the nature of the processes known in 

 Mymenolepis villosus, or young worms budded off from the 

 parent stock. There is very little, if indeed anything, to be 

 said in favour of the former view. It is true that a large out- 

 growth of the body to form a tentacle might have very much the 

 same structure as the body, even to possessing branches of the 

 excretory system and lateral nerve-cords. But there would 

 hardly be a practical identity of structure such as I shall point 

 out in detail later. Furthermore, the growth of processes of the 

 body might be expected to be more regular than are these out- 

 gi-owths (cf. text-fig. 113), and above all a gradual freeing of 

 themselves from firm contact with the body, as shown in the 

 figure, is precisely what we should expect with budding offspring, 

 which, as it appears to me, is the obvious and only way to in- 

 terpret these appendages of the fuUy grown worm. 



* Zool. Jahrb., Abth. f. Syst. Bd. xx. 1904, p. 131. 



