2-iG Prof. JPIntosirs Notes fro tn the 



having muscular fibres from the bristle-tuft attached to it ; 

 and the hypoderm is thiuued at the tuft and has au iucurva- 

 tiou at its upper edge, whilst it rapidly thickens above it. 

 Moreover, a distinct muscular slip (mc.) occurs in the mid- 

 ventral line, the remnant of the complex condition in front. 



The next change is the infolding of the stomachal wall 

 (PI. VIII. fig. 10, 5^.), the loss of its lateral connections, and 

 the termination of its cavity ; whilst the intestine enlarges, 

 its folds become more prominent and alter their character, 

 resembling, indeed, the oesophageal hypodermic lining. The 

 intestine still shows a plexus of vessels, about seven, for 

 instance, being cut on each side, and they resemble buds 

 from the investment of the gut, though they are only sections 

 of longitudinal trunks with their internal and external 

 investments. The dorsal mesentery and its enclosed vessel 

 now pass upward from the gut-wall, and inferiorly are the 

 ventral mesentery and its vessel, the membrane trending to 

 a fissure between the more massive ventral longitudinal 

 muscles, since the special median muscular area and its fibres 

 (shown in PI. Yill. fig. 7 a) have disappeared. The nerve- 

 cords are separated only by their own breadth from each 

 other, and they are, perhaps, more distinctly granular than 

 before. The mucous glands, with their secretion rendered 

 fibroid by preparation, are now prominent, each placed 

 above the ventral muscle of its side. The coelomic spaces 

 (PL IX. fig. 11, c), reduced to one on each side, have a 

 translucent coagulum with granules. 



When the nerve-cords touch and fuse (PI. IX. fig. 11, nc.) 

 it is seen tiiat the glandular tubes in the coelora approach 

 each side of the ventral vessel, and slope outward as they go 

 forward to the excretory duct below the bristle-tuft. Tlie 

 gut has become pear-shaped, the narrow end being below 

 Avith its mesentery, whilst two mesenteries pass from the 

 dorsal arch and join before reaching the dorsal blood-vessel. 

 This arrangement makes an additional supra-intestinal 

 chamber. 



The hypoderm still presents a symmetrical enlargement 

 ijnst above the bristle-tuft on each side, this thickened region 

 being differentiated by the narrow layer immediately above 

 it, for it gradually deepens dorsally and again becomes 

 narrow as it reaches the mid-dorsal line. Prom the lower 

 edge of the bristle-tuft it gently increases to the nerve-cords 

 in the mid-ventral line. The dorsal longitudinal muscles 

 are thinner than the massive ventral, but they extend over 

 a larger area of the body-wall. 



A little further back (PI. IX. fig. 1,2) tlie gut increases in 



