4:24: Piof. M'Intosh on the 



over the lougitudinal ventral muscle — on the ventral surface 

 of which it increases in depth, — to protect the nerve- trunk 

 situated in the hollow next the oblique muscle. The layer 

 then gradually diminishes toward the middle line, and, 

 passing over, follows tlie same arrangement on the opposite 

 side. The neural canal now lies on the ventral aspect of the 

 nerve-trunk. The thick layer on the lateral dorsal regions 

 has the hypodermic fibres directed upward and outward, 

 while the hbres in the ventral masses at the nerve-trunks 

 pass outward and downward. The hypodermic nerve-area 

 soon bcconies quite ventral in position, and the neural canal 

 is inferior and internal to the nerve. The latter is farther 

 protected by a thicker layer of cuticle than that on the 

 dorsum. Just below the inferior bristle-bundles (at tlie 

 lower edge of the attachment of the oblique muscle) a rather 

 constant fold of the hypoderra and cuticle occurs from the 

 fourth to about the eighth segment, and in transverse sections 

 a space (or canal) appears in the hypoderm. The granular 

 matter next the basement-tissue is also increased at this 

 point. 



The chief change that ensues in the anterior region of the 

 body is the gradual diminution of the hypodermic area 

 between the nerve-cords. The neural canals, leaving the 

 latter, glide inward to the middle line, first getting under 

 the convex bellies of the transverse muscles and then uniting 

 in the centre. The nerves still occupy a position on each 

 side under the point of attachment of the vertical and oblique 

 muscles. In regard to the disposition of the other parts 

 of the hypoderra it may be mentioned that besides the 

 increase at the nerve-cords, other thickenings occur at the 

 opposite points of the dorsal region in the preparations (viz. 

 at the dorsal end of the vertical muscular band). The 

 shortening and diminution of the transverse ventral muscle 

 toward the posterior end of the region permit the nerve-cords 

 to approach each other ; indeed, little hypoderm is left 

 between them around the median (neural) canal. In the 

 ninth segment the dorsal hypoderm is divided into a narrow 

 layer over the muscles and the two great dorsal lamelhie. 

 That on the lateral wall of the body has diminished in 

 depth^ but the ventral hypoderm is not much altered. Then 

 the great infero-lateral lamellae occupy the body-wall, and 

 confine the ventral hypoderm to a narrower area. Finally, 

 the dorsal layer diminishes in thickness and spreads outward, 

 so as to inaugurate the condition of the posterior region, 

 which consists of a very thin firm granular layer of hypo- 

 derm over the dorsal longitudinal muscles, with a deeper 



