191S] Alimentary Canal of Altica Larva 3,07 



We may summarize the distribution of the tubes in the 

 larva as follows (beginning at the distal end) : Six Malpighian 

 vessels extend parallel to one another, running cephalad in the 

 wall of the colon; they unite at the anterior end of this region 

 to form two common trunks, which, leaving the wall of the 

 intestine, split up into a single tube, and a common . stem 

 representing a pair of tubes; the single tube, which is very short 

 and delicate, runs directly to the ventriculus, where it is inserted 

 isolated into the wall of the intestine, just at the point where 

 the mid-intestine joins the hind-intestine; each common stem 

 soon splits up into two vessels, which have a long course through 

 the body-cavity, but eventually all four unite to form a single 

 common urinary bladder, which empties directly into the ileum, 

 at a point a little posterior to the insertion of the two shorter 

 tubes. 



For convenience in discussing the histological structure of the 

 tubes, the writer has spoken of that portion of the Malpighian 

 vessels enclosed in the walls of the colon, as the "included" 

 portion, and the part which lies free in the body cavity as the 

 'coelomic' " portion. This is of course a very free use of 

 the term, for the coelome, or true body-cavity, is very much 

 reduced in insects, and the apparent body-cavity is in reality 

 only a greatly enlarged haemocoele, or blood sinus. 



The Histological Structure of the Vessels of the 

 First Series. 



the "coelomic" portion. 



Proximal. Interiorly, the epithelial cells of the proximal 

 portion of the Malpighian tubes of the larva are covered by a 

 wide, lightly staining striated border, composed of many very 

 fine and closely appressed striae, beneath which is a narrow 

 band of dense deeply-staining cytoplasm. The cell cytoplasm, 

 which stains deep violet-pink with eosin, is very granular, and 

 presents a more or less fibrillar aspect. The nucleus, which is 

 proportionately large, varies in shape from elliptical to circular, 

 and is typically basal in position. The chromatin granules are 

 larger than those of the distal nuclei and are not so densely 

 compacted. They occur especially around the perifery. 



Vacuoles in these cells indicate a secretory activity, but 

 the writer has not followed the secretion cvcle. From the 



