No. 2.] NOTES ON DISTOMUM PATELLARE. 6 1 



sometimes seen which is traversed by delicate fibrils connect- 

 ing the two layers ; these fibrils are noted by Leuckart, 3 

 Brandes, 4 and Looss. lu) When the cuticle is torn away, the 

 fibrils break at the subcuticula. Their distribution and appear- 

 ance preclude the idea that they are inserting muscle fibrils or, 

 as Brandes suggests, the ducts of glands ; it seems probable 

 that they arise by the formation of vacuoles in the base of the 

 cuticle and indicate a close connection between cuticle and sub- 

 cuticula. The space traversed by these fibrils looks like a vacu- 

 olar layer and may correspond to the " vacuolar middle layer of 

 the cuticle " described by some authors (Monticelli, 5 E. Walter, 6 

 Poirier 7 ), their "basal layer of the cuticle" being what is here 

 called the limiting membrane of the subcuticula. When cuticle 

 meets epithelium it does not pass over it, under it, nor by tran- 

 sition into it, but ceases abruptly. There is in D. patcllare 

 no evidence that the cuticle is shed; the existence of well- 

 differentiated nerve-endings in the cuticle seems, indeed, evi- 

 dence to the contrary. 



The tissue between the cuticle and the subcuticular cells, 

 the subcuticula, has usually been described as undifferentiated. 

 In D. patcllare the outer part or limiting membrane is much 

 more distinct from the inner reticular part in some specimens, 

 where it is a thin, deeply staining sheet \ //, thick, than in 

 others, where it averages i //. thick, stains slightly, and passes 

 almost imperceptibly into the subjacent reticulum. The limit- 

 ing membrane forms sheaths for the inner surfaces of the 

 suckers, where it contains fibrils which are probably elastic ; it 

 receives the insertion of muscle fibrils, and passes by transition 

 into the basement membrane of ducts into whose external 

 openings it accompanies the cuticle. The fine meshwork of 

 the intermuscular reticulum, which shows no cellular structure 



3 LEUCKART, R.: Die Parasiten des Menschen, Aufl. ii, 1886. 



4 BRANDES, A.: Zum feineren Bau der Trematoden, Zeit. f. wiss. Zool., Bd. 

 liii, 1892. 



5 MONTICELLI, FR. SAV.: Studii sui Trematodi endoparassiti, Zool. Jahrbilcher, 

 Suppl. Ill, 1893. 



6 WALTER, E.: Untersuchungen iiber den Bau der Trematoden, Zeit. f. wiss. 

 Zool., Bd. Ixv, Heft 2, 1893. 



7 POIRIER, J.: Contribution a 1'histoire des Trematodes, Arch. d. Zool. exfer. 

 et gen., 2 ser., tome III, 1885. 



