396 MR, J. 15. GATENBY ON THE BIONOMICS, EMBRYOLOGY, 



(text-fig. 15^ p. 411) ; very careful observations were made with regard to 

 the lining of the mesenteron. In PI. 25. fig 10 the hinder region of the 

 mesenteron is drawn, in PL 25. fig. 11 the metathoracic region; in both 

 cases the same apparently chitinous intima is found. 



e. The Spinning Glands are remarkable ; they consist of two pairs of 

 tubular structures stretching from the buccal mass to the seventh or eighth 

 abdominal segment. In the region of the metathorax (X) the two pairs of 

 glands join up to form a single pair of ducts, which open into the inside of 

 the buccal opening (PL 24. fig. 6, SG). The silk glands, which as is well 

 known are modified salivary glands, are peculiarly and extremely well 

 developed in the Microgasteridse. In PL 25. fig. 11 the glands (SG) are cut 

 in transverse section. In PL 26. fig. 24 the right pair of glands and their 

 common duct (CD) are diagrammatically drawn. 



A.t the stage in PL 24. fig. 6 the Imaginal Discs are well developed. It is 

 not intended to describe them here at length ; in PL 24. fig. 6 there are 

 head-pairs at IDA, 3 leg-pairs at IDl to ID3, wing-pairs (W\ W^), and in 

 the posterior region of the body there are pairs [near the gonads, G in PL 24. 

 fig. 6]. It is these pairs which are of interest in this paper, for they provide 

 evidence with regard to the proper solution of the problem as to whether the 

 tern)inal vesicle is itself a seoment. The imaginal discs of the hind region 

 of the body are found in the segments marked 13 and 14 in PL 24. fig. 6. In 

 text-fig. 3 the imaginal discs could be seen on a level with the large ultimate 

 nerve-chain segment. No imaginal discs were seen in the vesicle. 



T. The Heart is not in any way peculiar in the front and main part of the 

 body of the larva (PL 25. fig. 11, H), but in the hind region within the 

 terminal vesicle it becomes modified. In PL 24. fig. 6 the heart is the white 

 line at H. In LI. 26. fig. 22 the transverse section of the vesicle shows that 

 the heart (H) is extremely wide here, and at each side of it is a bunch 

 of cells of a glandular nature. In amongst these cells are other larger 

 cells, which are blood corpuscles. The heart appears to open into the bulb 

 in several places, and the bunches of cells may be part of the mechanism of 

 valves. Towards the region where the bulb enters the eighth abdominal 

 segment the heart rapidly narrows, till further on, in the hinder abdominal 

 segments, it assumes its normal proportions. In PL 25. fig. 10 the heart, 

 which is just above the gut, does not probably lie in its normal position ; 

 this may be due to shrinkage, for it is a most diflacult matter to keep the 

 thin stretched bulb from becomino- distorted as the larvaB are being embedded. 

 In PL 25. fig. 10 the heart should lie just on or near the upper surface of the 

 gut, as in PL 26. figs. 22 and 24. 



cf. The Nervous System is not peculiar ; the only matter which need 

 interest us here is the question of the position of the last ganglia in the 



