500 University of California Publications in Zoology [Vol. 18 



Cercaria ocellata La Valette as described by Ssinitzin (1909, p. 316, 

 pi. 10, figs. 22, 23, 26). This author shows clearly the layer of circular 

 muscles of the posterior region of the oral sucker, the positions of 

 the ducts of the cephalic glands passing through the sucker and the 

 position of the mouth on its ventral surface. ]\Iost of the descriptions 

 of schistosome cercariae do not show the details of this organ. In 

 my figures (Cort, 1915, p. 50, pi. 7, figs. 59-62) of the oral sucker 

 of Cercaria douthitti the passage of the ducts of the cephalic glands 

 through the oral sucker is clearly brought out, although the other 

 parts are not entirely clear. In recent studies of an undescribed 

 species of schistosome cercaria with eyespots I found the structures of 

 the oral sucker to be much the same as in the cercaria of 8. japonicum, 

 including the thick circular muscular layer of the posterior region, 

 the head-gland, and the spines at the openings of the ducts of the 

 cephalic glands. 



The cephalic glands (figs. 1, 2, eg) are unicellular with large nuclei 

 filling almost all of the posterior half of the body. I counted five of 

 these glands on a side. The ducts from the cephalic glands pass 

 forward in two groups ventrad to the central nervous system and 

 digestive tract and enter the oral sucker as described above. These 

 glands are loose in texture, the bulk of each gland apparently consist- 

 ing of secretory products and are pushed into all sorts of shapes by 

 changes in the shape of the body of the cercaria. It is not easy to 

 distinguish clearlj^ the outlines of the cephalic glands and to determine 

 their exact number. Leiper (1915, p. 202) stated that there are five 

 or more of these glands on each side. I have, however, never noted 

 any variation in their number in different cercariae. Miyairi and 

 Suzuki (1914), Ogata (1914), and Miyagawa (1916, p. 66, pi. 4, fig. 

 30) noted only three pairs of these glands in their descriptions of the 

 cercaria of S. japonicum. Miyagawa 's figure (1916, fig. 30) shows the 

 cephalic glands as six small bodies between the digestive caeca and 

 the acetabulum, filling only a small part of the posterior body region. 

 ]\Iy observations lead me to believe that INIiyagawa's drawing is 

 incorrect in this particular. 



The total bulk of these glands and their ducts, which is more than 

 half the total bulk of the body of the cercaria, indicates that they 

 perform an important function. The cephalic glands of the fork- 

 tailed cercariae appear to be homologous to the stylet glands of the 

 xiphidio-cercariae which open at the base of the stylet or piercing 

 organ, and to which the function of dissolving tissue in connection 



