38 
ous corpuscles. The cells making up the embryo are at this stage 
irregularly disposed and all very small, except a few which are in 
immediate relation with the tail and primary cavity (lig. 55). Neither 
in this nor in succeeding stages was a subcuticular muscle system 
observed. 
61 
59 
62 
60 
Fig. 59. — Longitudinal and slightly oblique section of i/. nana after the invagination of its anterior 
portion; ac., sucker; hi. p., anterior opening of secondary cavity; 1. ext., external ■wall; 1. int., 
internal wall; pr, cav., primary cavity; ros^ rostellum. Enlarged. (After Grass! ct Rovelli, 1892a, 
pi. 3, fig. 17.) 
Fig. 60. — Embryo of if. nano. Same stage as preceding figure, in cross section at the level of the 
suckera: sec. cai\, secondary camty. Other letters as in preceding figure. Enlarged. (After 
Grass! & Rovelli, 1892a, pi. 3, fig. 18.) 
Fig. 61. — Longitudinal and slightly oblique section of an embryo of if. 7iana ac a stage somewliat 
later than fig. 59: ac., suckers; pr. car., primary cavity; ros., rostellum; sec. car., secondary cavity. 
Enlarged. (After Grassi & Rovelli, 1892a, pi. 3, fig. 19.) 
Fig. 62. — Transverse section of an embryo of if. iiana at the same stage as preceding figure. Enlarged. 
(After Grassi & Rovelli, 1892a, pi. 3, fig. 20.) 
The second stage., as observed iii the fresh state, still showed the 
cavity, and in the anterior part a deep, narrow, invaginated depression, 
shaped in longitudinal optical aection like an inverted Y (dg. 54), At 
this stage, also, there are more or less noticeable four points in which 
