Life-history and Anatomy of the Appendiculate Distomes. 371 



these authors probably believe in the existence of "Kopfdrüsen"; my 

 preparations seem to show that these single-celled glands are simply 

 modifications of the submuscular cells, resembling them in size, po- 

 sition, and staining qualities. 



My own opinion concerning the function of the submuscular cells 

 is that they are single-celled glands: but I do not believe that they 

 form the matrix of the cuticula, either in the manner advocated by 

 Beandes as secretors of cuticular substance, by Looss and Nicker- 

 SON as the source whence formed material moves outward when they 

 themselves develop into parenchymatous cells, or by Blochmann as 

 a hypodermis. Proof that these authors are mistaken is furnished by 

 the worm under discussion. The cells in question are present in the 

 entire trunk of the worm, but not in the appendix; yet the 

 appendix is furnished with a cuticula of exactly the same nature as 

 that of the trunk. I am satisfied, as already stated, that the cuticula 

 grows by additions from the entire body of the parenchyma, evenly 

 applied to its entire inner surface. 



But the submuscular cells, including the "Kopfdrüsen", although 

 they do not help to build u]) the cuticula, have a very important 

 function, for, in my opinion, they furnish a substance the purpose of 

 which is to render the cuticula immune from the disintegrating action 

 of the body-fluids of the host. I have already, in the description of 

 the cuticula (pag. 363), spoken of the probable effects of these fluids 

 on that membrane, and mentioned the fact that its external surface 

 often has a granular appearance, as if it were being attacked by 

 some disintegrating agent. The cuticula is a relatively soft membrane, 

 especially in its inner and middle portions, Looss calls it "ausser- 

 ordentlich elastisch und zähflüssig" and it quickly macerates after 

 death ; it would probably be quickly destroyed, and with it the softer 

 parts beneath , which it protects, if it were not protected by some 

 special means from the juices which surround it. The submuscular 

 gland-cells pour their secretion on the inner surface of the cuticula, 

 their ducts, where these exist, not extending through it to its outer 

 surface; and from its inner surface the secretion permeates every 

 part of it. The "Kopfdrüsen", on the other hand, pour tlieir secretion 

 on its outer surface, as their ducts do extend through it to the 

 outside. 



What the reaction of these secretions would be must dei)end upon 

 the nature of the fluid in which the worm is immersed. If it lives 

 in the stomach of its host, for instance, the reaction is probably 



