RESEARCHES IN HELMINTHOLOGV AND PARASITOLOGY. 22 1 



ter species is attributed to numerous marine fishes of European seas, 

 but among them neither the Shad nor Herring have been indicated, 

 Scolex pida appears to occur almost constantly in our vShad and Her- 

 ring. It was found along the course of the intestine, but especially 

 in the pyloric portion and in its appendages. Commonly not very 

 numerous, sometimes there were but few, but generally from about 

 a dozen to fifty and upwards. In the abundant mucus of the viscera 

 they appear as white granules, about the size of ordinary sand 

 grains. Their characters are as follows : In the quiescent condition 

 with the head withdrawn into the body ; spheroid, ovoid, ovate, or 

 cordate ; in front rounded or truncate and more or less emarginate 

 or projecting in a bipapillate manner ; posterior third conical, ob- 

 tuse or sub-acute, and annularly rugose. In the active condition 

 with the head projected, clavate, elongating and becoming linear 

 behind with the disappearance of the annular rugae. Head pro- 

 vided with four hemispherical bothria and a central spheroidal, cup- 

 like rostellum and with a bright red pigment streak on each side. 



i 3 



Measurements. —In the quiescent condition 0.5 to 0.625 nun. 

 diameter, or 0.5 to 0.75 and 0.875 mm. long by 0.375 to 0.5 mm. 

 broad, elongating without projection of the head to 1.125 mm. long, 

 0.375 mm. broad; with projected head to 1.5, 1.75, and 2.5 mm. 

 long by 0.25 and 0.2 mm. broad. Bothria 0.15 diameter; central 

 rostellum o. i mm. diameter. 



The accompanying figures, i, 2, 3, represent Scolex pida magni- 

 fied forty diameters; figures i, 2 in the quiescent condition, with 

 the head retracted ; figure 3 in the active condition, elongated and 

 with the head protruded. 



The Scolex when in motion, with the head retracted, elongates 

 and shortens and narrows and widens proportionately. In contrac. 



