ASCARIS LUMBEICOIDES. 303 



main it may be said that Ms descriptions were carefdl and accurate, 

 but some of tliem liave turned out erroneous. 



Commencing with the head, I remark, in the first place, that 

 the three prominent oral papillse are nearly uniform in size, their 

 occasional inequality being accidental. During life they are move- 

 able, and there can be no doubt that their combined action is suc- 

 torial. Viewed, from above, with a pocket-lens, the lips present 

 a tripetaloid figure, and, on a more close examination, they ex- 

 hibit, when separated from each other, a number of minute den- 

 ticulations at their inner surfaces. The oral aperture, without 

 any other special appendages, leads directly into a strong muscular 

 oesophagus, which in some specimens is fully half an inch in length. 

 A slight constriction separates this part of the canal from the stomach 

 and intestinal tract, these latter divisions of the tube not being 

 recognisable from one another. In fact, different anatomists have 

 variously interpreted the morphology of these parts ; but, since 

 many of the nematoda display an organ comparable to a true sto- 

 machal cavity, I think it better to regard this thin and spacious 

 portion of the canal as merely representing the intestine. To the 

 naked eye it displays a deep brown colour which is mainly due to 

 the intestinal contents, but as obtains in many allied species, the 

 epithelium and general cell wall are more or less supplied with 

 dark pigment granules. All I need here further say, is that the 

 alimentary canal, in both sexes, is terminated by a cloacal cavity, 

 which opens externally by a transverse slit at a very short distance 

 from the extremity of the tail. In this situation, one not unfi:'e- 

 quently finds a number of minute papillae on the surface of the body, 

 which do not make their appearance elsewhere. And this leads us 

 to examine the skin, which, notwithstanding all that has been said 

 to the contrary, really seems to me to consist of only two well- 

 marked layers, namely, an external chitinous and an internal granu- 

 lar layer. No doubt Czermak and others have been able to split 

 these layers into six or eight different laminae, but, after all, nothing 

 is gained by so many arbitrary divisions. The chitinous layer is 



