1^4 PATTEN AND REDENBAUGH. [Vol. XVI. 



bend near their proximal ends ; the proximal end of the 

 second haemal nerve is straight ; the third nerve has a slight 

 flexure ; the fourth has a greater one ; and the fifth and sixth 

 have very marked flexures. 



The median eye nerve (in.e.n) passes between the haemal 

 and the neural integumentary branches of the second, third, 

 fourth, and fifth haemal nerves. The first haemal nerve or 

 lateral nerve (/.«.) passes haemal to the second haemal nerve 

 and neural to all others. 



d. Nerves fro7n the Accessory Brain (Text-figs. 14 and 15). 



The accessory brain consists of two neuromeres fused 

 together, the seventh, or chilarial neuromere and the eighth, or 

 opercular neuromere. Both neuromeres have all the typical 

 elements, but they resemble the abdominal rather than the 

 cranial type. The haemal and neural nerves all arise from the 

 posterior side of the brain, and together with the ventral cord 

 pass through the occipital ring. 



(i) Neural Nerves. — The neural nerves of the two neuro- 

 meres differ so much from each other that it will be necessary 

 to describe them separately. 



(a) Chilarial Nerve. — The paired chilarial nerve (Text-fig. 

 14; Pis. VI-VIII, and X, Figs. 1-3, 11, and 12, n.n.^) arises 

 from the posterior side of the brain near the median line and 

 neural to the origin of the ventral cord iy.c). It passes poste- 

 riorly near the median line close beneath the roof of the occipital 

 ring {oc.r) into the chilarium. As it enters the base of the 

 appendage, it gives off branches to all the muscles of the 

 chilarium. The main nerve breaks up inside the appendage, 

 supplies the epidermis, and sends a large fiber into each of the 

 gustatory spines which fringe its inner margin. 



(b) Opercular Nei"ve. — The opercular nerve (Text-figs. 14 

 and 15 ; Pis. VI-VIII, and X, Figs. 1-3, 1 1, and 12, n.n.^) arises 

 just posterior to the chilarial nerve and passes backwards through 

 the occipital ring near the median line neural to the ventral cord. 

 At the base of the operculum {ap.^) it gives off a small branch 

 to the internal branchial muscle (Text-fig. 12, i.b.vi.) and then 



