1919] Cort: TliG Cercaria of the Japanese Blood Flulie 501 



with the penetration of the cercaria into its host has been ascribed by 

 certain authors. A full account of the functioning of the stylet glands 

 in penetration was given almost twenty-five years ago by Looss (1894, 

 pp. 127, 238). Faust (1918, p. 34), following La Rue's analysis (1917, 

 p. 5) of similar glands in an agamodistome, calls the cephalic glands 

 of the fork-tailed cercariae mucin glands. Miyagawa (1916, p. 366), 

 following Miyairi and Suzuki (1914), called the cephalic glands of 

 the cercaria of 8. japonicum "poison glands." I prefer the term 

 cephalic gland, since the ducts of these glands open at the anterior 

 tip of the cercaria. My studies lead me to believe that these cephalic 

 glands function in penetration, probably by dissolving tissue. Instead 

 of a single stylet as in the xiphidio-cercariae, the schistosome cercariae 

 have a number of spines around the openings of the cephalic glands 

 which perform the same function as the stylet in penetration. Besides 

 producing a cytolytic secretion which dissolves the tissues of the host 

 and thus aids the cercaria in penetration, it seems probable that the 

 secretions of these glands neutralize the toxic secretions that the host 

 produces in its attempt to combat the entrance of the cercariae. 

 Miyagawa (1916, p. 66) stated that these glands must have something 

 to do with penetration since, according to his observations, they dis- 

 appear soon after the cercaria has entered the body of the host. 

 Leiper (1915, part III, p. 260) also suggested that these glands in the 

 cercaria of 8. kaeniatohium function in penetration. The head-gland 

 which also disappears after the cercaria has entered the body of its 

 host, seems also to function in penetration. The productions of 

 eosonophil cells by the host in connection with the penetration of 

 the schistosome cercaria, suggests that the host is actively combating 

 the entrance of the parasite by the production of toxins. This may 

 be taken as evidence of the battle which is waged between the host 

 and the entering parasite. It seems to me very probable that the 

 head-gland and the cephalic glands are the batteries of the cercaria 

 in this fight, which in the offensive of the human schistosome cercariae 

 give such striking success to the invaders. Certain of the movements 

 of the anterior end of the cercaria of S. japonicum observed in con- 

 nection with the activities of the living animal support the theory that 

 the cephalic glands function in penetration. This evidence will be 

 brought out in connection with the discussion of the activity of the 

 living cercaria. 



