AND THE CLASSIFICATION OF WORMS". 7 



though as far as I am aware, there is no special statement published concerning an epithe- 

 lial lining of the oesophageal and pharyngeal regions in Trematods. I have again and 

 again had occasion to observe the destruction of the intestinal epithelium in various worms 

 by the action of alcohol and other hardening fluids, and for the present I must therefore 

 assume that the same cause explains the absence of the epithelium in the specimens I have 

 examined. 



The two coecal branches (figs. 1 and 3, D) are lined by a very distinct and beautiful 

 epithelium (fig. 12, A, transverse section of the wall of the ccecum), consisting of short, 

 broad, cylindrical cells, containing each a proportionately large oval nucleus. The nuclei lie 

 in the middle or basal portion of the cells, never in the upper part, and have sometimes 

 one, more frequently two, highly retractile, eccentric nucleoli. The protoplasm of the cells 

 is granular, the upper part is more deeply stained by carmine than the lower. In some of 

 my preparations this epithelium is cut parallel to its surface ; fig. 12, B, represents such a 

 spot. The amount of intercellular substance is small, and the cells present polygonal out- 

 lines, and are four, five, or six-sided. The epithelium, as is shown in fig. 12, A, rests upon 

 a basement membrane. The muscular layers outside are reduced to a few fibres running 

 in various directions, but apparently mostly circular. A similar epithelium to the one here 

 described I have found in several other Trematods, so that it may be considered character- 

 istic of the class. It is very different from the intestinal epithelium in Planarians, and as 

 far as I know, from that in any other class of worms. 



There are a great many unicellular glands in the anterior part of the body. They are 

 bottle-shaped (fig. 14), their necks running out towards the oval sucker. Their contents 

 appear collected, as seen in the figure, almost exclusively on one side, forming there a very 

 dark stained, finely granulated mass enclosing a relatively small nucleus, which can only 

 be detected by close examination. The other half of the cells is quite clear and colorless. 

 Is it not probable that this peculiar distribution of the granular matter is caused by the 

 alcohol producing a contraction of the cell-contents ? The body of the cells is very 

 large, and rounded at one end, while it tapers gradually towards the other, till it runs over 

 into a long narrow tube, which may be called the duct. The cell membrane is very dis- 

 tinct. The cells are distributed further back on the ventral, than on the dorsal side. 

 Transverse sections show the nuclei much more distinctly than longitudinal ones do. In a 

 section through the hind end of the oral sucker (fig. 2), the ducts of the ventrally placed 

 cells may be seen at each side, while the bodies of cells situated dorsally are seen crowded 

 together in the upper part of the section. These glands are undoubted homologous with 

 the so-called " Speichel-drtisen " of German authors, first mentioned by Walter, 1 and since 

 then observed by various other writers. 2 Similar glands are said to exist in various Pha- 

 ryngoccela, but I have not observed them in any of the Planarians I have investigated. 



The great development of the uterus, and the large number of eggs contained in it, 

 effectually hide some parts of the sexual apparatus, my description of which will therefore 

 be somewhat incomplete. 



1 Walter. Zeitschr. Wiss. Zool. Bd. vm,p. 198-199; and 2 Leuckart. Parasiten, I, p, 470. 



Archiv fur Naturgeseh. 24 Jahrg. Bd. 1, (1858) p. 291-292. 



