Mr. J. Lubbock on the Digestive System o/Coccus hesperidum. 307 



stomach, and a long intestine. Into this intestine open four glands. 

 Rather behind the middle of it are situated the two large, yellow 

 hepatic glands, and in front of these open, on one side, a free, slightly 

 curved caecum, and on the other, a shorter caecum coiled up and en- 

 closed in a pyriform sac, which is continued into a tube, whose end is 

 attached to the skin. This description is a singular mixture of truth 

 and error, and Professor Leydig is so careful an observer that it 

 was long before I could convince myself that he had made such a 

 series of mistakes. His descriptions of the separate parts are indeed 

 correct (though in my specimens the hepatic glands (G, G) were pro- 

 portionally larger than in his figure), but he has entirely misunder- 

 stood the relations of the diiferent organs. 



The true oesophagus (fig. 1 A) is rather long and extremely 

 narrow. It corresponds, I believe, to the tube / in Leydig' s figure, 

 which he considers as an appendage to the intestine. Following the 

 oesophagus comes the pear-shaped bag (fig. 1 F), with its remarkable 

 cellular, contorted, internal gland. Then there is a very short 

 intestine (D, ilium) opening into the rectum (C), which Leydig has 

 described as the stomach. The rectum is often found filled with 

 fluid, as Leydig figures it, and varies in shape in different specimens ; 

 it contracts at its posterior end into a narrow tube, B (the oesopha- 

 gus of Leydig), which opens into the vent on the upper side of the 

 body. 



At the anterior end of the pear-shaped crop or stomach are 

 attached, besides the oesophagus, the two ends of the recurrent 

 intestine (H), and the caecum (E), which is generally swollen at its 

 base, and is perhaps the equivalent of the sucking stomach. 



The recurrent intestine is considered by Burmeister and Lacor- 

 daire to be part of the ventriculus, but in all insects the Malpighian 

 vessels open into the duodenum, or, when this is wanting, into the 

 ilium, close behind the pylorus ; and as in the Homoptera they are 

 attached to the recurrent intestine, it seems improper to consider 

 this as part of the ventriculus. If the recurrent intestine be cut, a 

 number of large cells, some with daughter-cells, exude from it. 



According to Burmeister, the Malpighian vessels are never less 

 than four in number ; and according to Lacordaire, when there are 

 only two, they are always attached by both ends ; but in C. hespe- 

 ridum there are but two, and they are attached only at one end. 



It seems to me evident that M. Leydig must have detached the 

 whole canal from the skin, and, in doing so, ruptured the recurrent 

 intestine. In this case it would be very natural for him to regard 

 the free end of the longer part as the anus. The large rectum he 

 has evidently mistaken for the stomach, and the vent for the mouth. 

 There would then remain the oesophagus, which he has correctly 

 described as going to the skin. 



I have repeatedly dissected out the intestinal canal without rup- 

 turing the recurrent intestine ; and it may be observed that the 

 structure of the whole digestive organs, as now described, is in 

 accordance with that of the other Homoptera, which would not be 

 the case if M. Leydig is correct. 



20* 



