455 



caeca; but as the larva grows they increase in size, and over- 

 lapping as they grow, eventually form an elongated, well- 

 defined organ on either side o-f the intestine. 



In the larva eight hours after defaecation a general dis- 

 integration of these cells begins. In places the cytoplasm and 

 nucleus may degenerate into a fine powder and be cast into 

 the blood. In other places the chromatin of the great nucleus 

 clumps together in numerous small balls (fig. 170), and the 

 cell cytoplasm, with these degenerate chromatic globules scat- 

 tered through it, floats for a time in the semi-fluid contents 

 of the abdomen, and finally, sometimes by the intervention of 

 leucocytes, at other times by the chemical action of the blood, 

 disintegrates. At other times the apparently normal cells 

 may be observed, as late as twelve, or even sixteen hours after 

 defaecation, to become the prey of the leucocytes; numbers of 

 these have penetrated along a channel where the hepatic 

 caeca have prevented the fat-body from, encroaching too much 

 upon the intestine, and here they fall upon the great hyper- 

 trophied cells, and a few hours later nothing but groups of 

 leucocytes, and a little debris, remains to indicate the place 

 where these gland cells have once been (fig. 147, 1). 



Just what these organs are I am unable to say. Their 

 structure is similar to that usually seen in gland cells; the 

 absence of any duct communicating in any way with the 

 intestine or any other organ, indicates that they are structures 

 analogous with the various internally secreting glands so well 

 kno wn in vert ebrates. 



The Dorsal Abdominal Glands. '^- 



These glands are to be observed in their mature condition 

 only in the imago; it is not impossible that they have the 

 same function here as the lateral intestinal glands have in 

 the larva. 



In the early larva they are to be observed as a single 

 flat band of small closely packed cells, lying upon the mid- 

 dorsal region of the intestine in the hinder part of the 

 abdomen (fig. 173). They show a clear cytoplsism and are 

 undoubtedly in an embryonic condition. But during larval 

 life they grow considerably, and separating from one another 

 form a pair of long chains on either side of the heart.^ One 

 ojTthese is shown in fig. 213. In the defaecating larva they 

 are quite large, measuring 20/x in diameter. They are 

 approximately spherical; their nucleus is branched, and their 

 cytoplasm very vacuolated; during the remainder of larval 

 life they grow a little in size, and are not unlike the 

 degenerate fat cells of the late pupa in appearance (fig. 172). 

 Nevertheless, they are in no way to be regarded as embryonic 

 fat cells. 



