398 ME. J. B. GATENBY ON THE BIONOMICS, EMBRYOLOGY, 



manner into a large number of processes which in section look like the teeth 

 o£ a comb. These processes rest on a layer which seems in some cases to be 

 a cell-wall, in others a layer ol: connective-tissue cells finely drawn out; 

 at all events the teeth of the comb are joined together by a distinct line as 

 drawn in PI. 25. fig. 12. The inside of the vesicle is lined by a network 

 of connective-tissue cells which join on to muscle bannerets and to the 

 cardiac region. 



In PI. 25. fig. 14: is a part of the vesicle-wall drawn at a lower power 

 than fig. 12, from material fixed in Giison-Petrunkewitsch. The outer 

 chitinous layer is thicker than in the case of fig. 12, there are the same cell 

 processes, but at F.E., where in fig. 12 was the outer granular layer, is a 

 curiously frilled edge to each cell ; no granular layer could be found, and 

 the exact relationship of the frilled layer and the granular layer is difficult 

 to ascertain. 



In PI. 25. fig. 13^ a part of the ordinary body-wall in the mid-abdominal 

 region is drawn, and is magnified the same amount as PI. 25. fig. 12. The 

 immense size and thickness of the vesicle cells now become clear. Fig. 13 

 represents the ordinary type of hypoderm found in Hymenopterous and 

 other insect larvse. 



Seurat (13) described a pair of Malpighian tubes in his larvse; what ho 

 supposed to be Malpighian tubes are not connected to the gut, but are the 

 tubes marked Tx in PI. 24. fig. 6. The most careful search in sections and 

 whole mounts failed to reveal any typical Malpighian tubes^ and Seurat 

 has made a mistake (see page 399). Sections of the vesicle, however, show 

 two organs very like Malpighian tubes. These Vesicle Glands are shown in 

 PL 26. fig. 22 GLj in a transverse section of the hinder region of the vesicle. 

 At Tx are cut the structures thought by Seurat to be Malpighian tubules. 

 The vesicle glands are a pair of somewhat coiled tubes which open to the 

 epidermis on the dorsal region at each side of the dorsal vessel (heart). 



In PI. 26. fig. 20 is a diagrammatic plan of a section of the region just 

 where the bulb joins the ninth abdominal segment; this region is between 

 the letters M— in PI. 24. fig. 6. In the section in PI. 26. fig. 20, dorsal 

 and ventral are shown by the letters D and V. The heart is at H, the gut 

 at GTj the vesicle glands are at GL in the form of black dots (in section), 

 and at the region X at each side of the heart the duct opens to the exterior. 

 The region X is drawn in PI. 26. fig. 19 at a high power. The gland is at 

 GTj, the heart at H and the opening at 0. The region above the heart 

 is just here flattened or even depressed in a peculiar manner as shown in 

 PI. 24. fig. 19, and it is just where the ordinary enlarged vesicle cells join 

 the flattened region that the vesicle glands open to the exterior (compare 

 fig. 19 and fig. 20). The vesicle glands stain darker than the epidermis 

 (hypoderm). In PI. 24. fig. 6 the vesicle glands are seen at GL, the 

 opening at 0. In PI. 26. fig. 21, is drawn a transverse section of the vesicle 



