1916] Malpighian Vessels of Haltica Biniarginata 403 



fig. 1) one would also infer that there was a fusion of the three 

 vessels and not simply an apposition. However, Gorka 

 states that under high magnification, even without sectioning 

 it can be seen in Gnaptor that the fusion is only apparent and 

 not real. 



In H. bimarginata there is a bladder and- a dimorphism of 

 the vessels correlated with a difference in their insertion and 

 in their length, features no one of which is found in Gnaptor. 

 Finally it is very clear in Haltica that the vessels pass into the 

 wall of the colon, while from the figures of Gnaptor it seems 

 equally clear that it is actually the wall of the rectum into 

 which the vessels penetrate. It is evidently the colon into 

 which the Malpighian tubes pass in all of the figures of chryso- 

 melid aHmentary canals drawn by Ramdohr (1811) and Dufour 

 (1823-25, 1840, 1843). 



Moreover the vessels of the alder flea beetle are very clearly 

 appendages of the hind intestine and not of the mid-inte.stine. 

 One would need very conclusive embryological data to be 

 convinced that the Malpighian vessels were really appendages 

 of the mid-intestine and not merely associated with it 

 secondarily. 



4. THE FUNCTION OF THAT PORTION OF THE TUBES ASSOCIATED 

 WITH THE WALL OF THE COLON. 



While working on the larvae of Galleria mellonella (Lep- 

 idoptera) in 1908, Metalnikov demonstrated that the cells in 

 the "tubes contournees" (as he termed that portion of the 

 Malpighian vessels associated with the wall of the colon) 

 never pass through the cycHc changes characteristic of the cells 

 of the free portion of the vessels, and indicatory of secretory 

 activity, nor do they take up any coloring agents injected into 

 the body cavity. He formulated the hypothesis that this part 

 of the tubes constitutes a special excretory apparatus which 

 ehminates such toxic substances as may have passed through 

 the intestinal epithelium. 



This is the opinion of Poyarkoff (1910) and substantially 

 that of Gorka (1914) who further confirmed the fact that there 

 is a difference in the reactions and function between the portion 

 of the tubes lying free in the body cavity and the portion 

 associated with the hind intestine. 



