I 



M. Van Beneden on a new genus of Cestoid Worm. 43 



Second, or Strobiloid. The body elongated, flattened, termi- 

 nated by a distinct head, assuming the form of a hammer, and 

 having two rows of hooks ; neck supporting three rows of spines 

 on each side. The lemniscus protrudes in the median line. Length 

 of worm 5 to 6 millimetres. 



Third, or Proglottnid. Body elongated, rounded, no external 

 opening except that for the lemniscus to escape ; lemniscus rugose 

 at the base, and when unrolled nearly as long as the body. 

 Length of body 1 millimetre. Ova very minute, y^o^h of a mil- 

 limetre in diameter. 



Echinobothrium typus. Scolexoid stage unknown. In the 

 Strobiloid, a distinct head, neck and trunk exist. The general 

 form is that of Helminthoid worms, — that one mostly assumed 

 by naturalists to be the perfect condition of such beings. 



The head resembles in its great mobility that of Scolex, or of 

 Tetrarkynchus. It may elongate itself into the figure of an arrow- 

 head, or become contracted into a rounded form; and such 

 changes take place with astonishing rapidity. The head is flat- 

 tened like the rest of the body, and has two overlying very con- 

 tractile fleshy lobes applied to one another. Within the head 

 and towards its fore-part lies a bulb, rather more transparent 

 than the surrounding tissues, and supporting two rows of hooks, 

 one beneath the other, as seen on viewing the flat surface of the 

 head. This bulb expands itself abruptly, giving off" a process on 

 each side the head, which then resembles in figure that of the 

 hammer-headed shark. The hooks previously seen within the 

 head now fringe the extremities of these processes, and in situa- 

 tion resemble that of the eyes of the fish just named. This ap- 

 pearance is to be seen only in certain positions of the head. 



Nine of these hooks have been counted disposed in one row ; 

 they are all of about the same length and shape, tapering to a 

 point which is curved inwards, and exhibit near their middle a 

 slight enlargement. They are very readily detached. 



In the interior of the head, posterior to, and nearer the sur- 

 face than the bulb, are four flexuose cords, extending thence to 

 the last joint of the animal. These cords resemble those met 

 with in most Tenioid worms, and which M. E. Blanchard has, in 

 some examples, succeeded in injecting. 



The neck is clearly defined by constrictions, from the head in 

 front and the trunk behind. It is nearly as long as the head, 

 flattened like it, but narrower ; and on each side is armed with 

 three rows of spines, in which circumstance this worm difi'ers 

 from all other Helminths. The spines are nearly of the same 

 length, straight, tapering, with a trifid base imbedded in the soft 

 substance of the animal. Each row has twelve to thirteen closely 



