2io DISCOVERY REPORTS 



Muscle 4 runs from the top end of the tripod to attach to the mid-lateral body wall 

 (Plate XLII, fig. 9). Muscle 5 attaches anteriorly just below muscle 4, but runs backwards 

 to end on the upward branch of the e sclerite. Muscle 5 thus runs between two points 

 directly connected by a skeletal rod system consisting of the abc sclerite, the lateral 

 brace, and the e sclerite. If this system were not flexible the muscle would be useless. 

 These two muscles, 4 and 5, must have a leverage action about the fixed point at the 

 anterior end of the lateral brace, partly raising and partly pulling back the front part 

 of the body. 



Muscle 6 runs from the c sclerite to attach to the adductor tendon. This will similarly 

 have a leverage action, but will lower and push forward the front part of the body. 

 Muscle 6 can thus be looked upon as antagonistic to muscles 4 and 5. 



Muscle 7 runs from the lateral extension of the antenno-labral apodeme backwards 

 and outwards to the hinder end of the lateral brace. Muscle 8 runs from the adductor 

 tendon to the upper posterior arm of the e sclerite, while muscle 9 runs from a similar 

 place to the lower branch of the same sclerite. These muscles can all be seen, although 

 they are not numbered, in Fig. 6. They are approximated parallel, and could assist 

 the dorso-ventral body retractors in withdrawing the body inwards. Probably, however, 

 they are not related to their function. Muscle 7 will have a powerful effect in pulling 

 backward the median parts of the antennal attachments, while muscles 8 and 9 must 

 represent a pair of antagonistic muscles capable of moving the attachment of the second 

 trunk limb about the hind end of the e sclerite. 



Muscle 10 is the dorso-ventral body retractor, the function of which I have already 

 described (Fig. 8). 



Muscle 1 1 (Plate XLII, fig. 5) runs from the anterior end of the lateral brace to attach 

 alongside muscle 4 on the mid-lateral body wall. It probably functions in supporting 

 this region of the body wall, a region which, as I shall explain in that part dealing with 

 the blood system, is of great importance. 



Muscle 12 runs from the a sclerite to the lateral extension of the antenno-labral 

 apodeme as a depressor to the abc sclerite. 



There is one more sclerite in the anterior system to be mentioned — the / sclerite — 

 which appears to be qtiite independent of the rest. I mentioned it in Doloria but was 

 unable to settle its extent accurately. It runs from the adductor tendon backwards and 

 outwards to the body wall above the upper end of the vibratory plate of the maxilla 

 (Fig. 6), but it has no connexion with the e sclerite (Figs. 4-6). About the middle of 

 its length it bears an articulated sclerite which projects downwards and supports the 

 vibratory plate of the maxilla, but as this can only be seen from an outside view of 

 a sagittal half, it does not appear in Figs. 3 and 4. 



Associated in a peculiar way with the / sclerite is a large and complicated apodeme 

 which projects inwards between the maxillule and maxilla (Figs. 4-6). As this apodeme 

 only appears to support the musculature of these limbs, it has not been coloured like 

 the rest of the system, but it sends backwards an extension which curves over the top 

 of the /sclerite and is attached to it at this point. In potash preparations the two struc- 



