Life-history and Anatomy of tiie Appendiculate Distomes. 365 



like layer composed of inditierent, parenchymatous cells to be present 

 just beneath the superficial muscle layers, which develops into the 

 highly vacuolated parenchyma towards the inside, and, towards the 

 outside, secretes cuticular substance. It is in the submuscular cells 

 that he sees this cambium-like layer, in other words in the layer which 

 forms the single- celled, cuticular glands of Brandes and the modified 

 hypodermis of Blochmann. He differs from these authors, however, 

 in that he does not believe in the existence of definite ducts con- 

 necting the submuscular cells with the cuticula, but holds that the 

 material they secrete passes through the superficial muscle-layers and 

 thus reaches it. But, notwithstanding this difference, the interpret- 

 ations of these three authors of the physiological significance of the 

 submuscular cells are identical. 



The proofs which Looss (1894, p. 122) adduces to show that 

 material does actually pass from the entire subcuticular region into 

 the cuticula, and those which Nickerson (1894, p. 454) also adduces 

 in support of the same fact, seem to me conclusive, but they do 

 not prove that the matter in question comes from the 

 submuscular cells. Both of these authors show that pigment 

 granules and other minute structures, which are often present in the 

 subcuticular region, may be detected at times imbedded in the inner 

 surface ot the cuticula, and even within the body of that membrane, 

 as if they were being moved progressively outward. To me these ob- 

 servations simply prove that the entire peripheral portion of the par- 

 enchyma is producing cuticular substance. 



I can add an observation which seems equally conclusive of the 

 same fact. One of my students, Mr. J. W. Taylor, has recently 

 made a series of sections of the large Fasciola magna which are 

 stained with the Btondi-Heidenhain three-color stain. The cuticula 

 of this worm is very thin over certain portions of its body; large 

 spines are present at these places, the bases of which, accompanied 

 by the innermost layer of the cuticula, project far back among the 

 superficial muscles. There would thus be an inconsiderable formation 

 of cuticular substance in these places except just beneath the spines, 

 where it would be very active. We often find, consequently, beneath 

 the base of a spine radially diverging lines extending from it into the 

 surrounding tissues which I hold to indicate that matter is streaming 

 into the base of the spine from the entire body of the parenchyma 

 in the vicinity. My own interpretation of the submuscular cells will 

 be given when I speak of the parenchyma (p. 369). 



