354 THE GROUSE IN HEALTH AND IN DISEASE 



The abdominal stigmata are twelve in number, there being a pair on the second 

 to the seventh segment, both included. They lie on little eminences, like a tee on 

 a teeing-ground, situated about one-sixth of the body-breadth from the edge, and 

 from each is given off a short trachea which soon splits into two branches. Of 

 these the posterior splits up into innumerable fine twigs, which supply the various 

 organs of the segment, and the anterior runs almost straight into the longitudinal 

 trunk, thus placing the system connected with one stigma in communication with 

 all the others on the same sides of the body. By this means, if one stigma be 

 blocked the organs it supplies are not deprived of air, but receive it from another 

 system. The smaller tubes on each side pass across the middle line, and seem to 

 place the right and left systems in communication. In Menopon titan, according 

 to Snodgrass, the right and left systems communicate by means of a large transverse 

 trunk in the fourth abdominal segment. The spiral thickenings are well marked. 



Grosse has described just within the mouth a dorsal and a ventral piece of a 

 Alimentary " Schlundskelet." Unless the lyriform organ, or " cesophageal sclerite," 

 represents the ventral piece, this structure is not evident except in sections. 

 The oesophagus is a simple tube with muscular walls which traverses the posterior 

 part of the head and the thorax. Soon after it reaches the abdomen it gives off a 

 blind pouch or crop, which is always choked with feathers, and forms the conspicuous 

 black patch which shines through the wall of the abdomen. The walls are very 

 muscular, both longitudinal and circular muscle-fibres being conspicuous. It usually 

 lies near the middle line, but somewhat obliquely, and pointing posteriorly to the 

 right. Behind the point where the crop is given off the stomach or chylific ventricle 

 passes backward, lying to the right of the crop. At the posterior end of this the 

 four Malpighian tubules arise, and then there follows a short intestine in which 

 usually masses of undigested feather-fragments are to be seen. The intestine is 

 short, and ends in a ring of six almost spherical bodies. Each of these seems to 

 consist of a single gigantic cell, and the whole is very richly supplied with tracheae. 

 These bodies closely resemble similar structures found in the rectum of many Diptera, 

 e.g., the blow-fly and the mosquito. Behind them there is a short rectum, which 

 ends in an anus situated beneath the terminal plate. Numerous muscles run from 

 the body-walls of the last two segments to be inserted into the rectum, and doubt- 

 less act as divaricators. 



The excretory system consists of (a) the Malpighian tubules, and (6) the fat- 

 Excretory body, in which nitrogenous waste matter is often stored away. The 

 system. Malpighian vessels are four in number ; they arise at the interior end 



