AND ANATOMY OF CEETAIN HYMENOPTERA PARASITICA. 399 



gland. It looks exactly like a Malpiohian tubule, and in its length it 

 is covered by a layer of epithelial cells (maybe mesoderm) which are 

 shown in fig. 21. There are four or five cells in the transverse section 

 of the gland tube, but no crystals or urates could be seen in the gland cells. 

 The origin of the gland could not be worked out, but it is probably an 

 epidermal ingrowth. In PL 26. fig. 24, the gland is shown diagrammati- 

 cally at GL, the opening at 0. (See also page 411.) 



i. The body-cavity of the larva is occupied by a large Fat-hody which is 

 shown in PI. 25. figs. 10 & 11, F.B. No fat-cells are found in the vesicle 

 during early or middle larval life. The fat-body is of the usual type found 

 in hymenopterous larvse. The nuclei are somewhat branched, and the fat- 

 body lies in the form of several lobes. 



In PI. 24. fig. 6 the fat-body is not drawn, but it would pack around the 

 various tubes and glands drawn from the letter ID 1 to the letter G. 



Tlie Tracheal System. 

 In the adult larva there are seven stigmata, as in text.-fig. 1. The first is 

 on the metathorax, the rest follow on the other abdominal segments behind. 

 The last stigma is on the sixth abdominal segment. Seurat says other 

 stigmata exist, and mentions that just before pupation of Microgaster another 

 stigma opens. In PL 24. fig. 6 the tracheal system is drawn in, somewhat 

 diagrammatically. The two lateral trunks (T) give rise to at least seven 

 stigmal trunks (1st S, 7th S), but for any others I cannot speak. Seurat 

 describes in all nine stigmal trunks, but my text-figs. 1 and 2 do not aoree 

 with his description quoted by me on page 391. I regard my evidence, 

 gathered as it is from sections, potash preparations, and from whole 

 preparations, as irrefutable especially with regard to the stigmata in the 

 adult larva. Seurat's account seems based particularly on Microplitis, and 

 quite possibly his statement that the tracheal systems of all the Micro- 

 gasteridse is similar, may be incorrect. This would account for my inability 

 to agree with his description of Microplitis seurati. 



The MalpigUan Tubes (?) of Seurat. 



If PL 24. fig. 6 be examined it" will be seen that two tubes are to be found 

 running parallel to the hinder region of the gut, marked Tx. At the vesicle 

 region they join the vesicle wall at Tx. In. PL 25. fig. 10 these tubes were 

 not cut in the obliquely sagittal section, but I have drawn the left-hand one 

 in at Tx to show its relations with the gut. These tubes do not join the gut 

 at any part of their length. They end near the first abdominal segment, 

 where they taper more or less to a point. This last fact is rather important. 

 I will call these two tubes the " enigmatic tubular glands," till their true 



