PHYSIOLOGY OF THE INVERTEBRATA. 259 



The Nematoidea. 



In a paper read before the Royal Society of Edinburgh on 

 July I, 1889, the author stated the results of his examina- 

 tion of the renal organs of the Nematoidea. 



The body of the " thread-worms " is elongated, round, and 

 thread-like, tapering (more or less) towards the anterior and 

 posterior ends. The Nematoidea are not divided into segments, 

 and they have no segmental organs. 



In the species {Awjuillula hrevupinus) selected for investi- 

 gation the renal orsran is a glandular mass situated in front 

 of the gizzard. This organ has a well-developed excretory 

 duct, which opens externally by a trauverse slit (the vascular 

 pore) on the ventral side of the body. 



When a section of the glandular organ of AnguiUida is 

 examined under the microscope, the epithelial lining is seen to 

 consist of nucleated cells, similar to those of the Malpighian 

 tubules of the Inseefa (see later in this chapter). 



The organ contains a clear fluid, wdiich can be made to yield 

 microscopic crystals of uric acid. The author has extracted 

 uric acid from a large number of these organs (obtained by 

 dissection under the microscope) by boiling them in distilled 

 water. The filtrate, tested by the methods already described, 

 yielded uric acid and murexide crystals. 



A fresh " glandular organ " was placed upon a microscope 

 slide and crushed ; then a drop of dilute acetic acid added, and 

 the whole covered by a cover-glass. On examiniug with the 

 microscope it was observed that rhombic plates and other 

 crystalline forms had deposited. The cover-glass was slightly 

 raised, and on the addition of a drop of nitric acid, followed 

 by ammonia and gently heating over a spirit lamp, prismatic 

 crvstals of murexide were formed. 



No urea, guanin, calcium phosphate, &c., could be de- 

 tected in the excretion of this organ. 



These reactions prove that the so-called " glandular organ " 

 of the Nematoidea is physiologically a kidney. 



