144 PATTEN AND REDENBAUGH. [Vol. XVI. 



sensory, lie opposite each other in a channel through which a 

 continuous current of water passes when the gills are being 

 aerated. 



This nerve differs so much in character from the other haemal 

 nerves that it might be considered as an entirely different nerve. 

 Its origin seems to correspond with the origins of the haemal 

 nerve of the typical cranial neuromere, and it passes anterior 

 to the tergo-coxal muscles of the chelicera, just as the haemal 

 nerves of the other neuromeres pass anterior to the tergo-coxal 

 muscles of their own metamere. Its fusion with the second 

 haemal nerve, and its intrusions into all the succeeding meta- 

 meres without communicating with the haemal nerves, are 

 peculiarities which differentiate it from the other haemal 

 nerves. 



It was first described by Owen as a branch of the second 

 haemal nerve, but he did not trace it into the abdominal region. 

 Milne-Edwards overlooked it entirely. Viallanes, in his figure 

 of the brain, figures the root of it and designates it as the 

 recurrent nerve. Patten did not describe its distribution, but 

 in his figure of the brain represented its proximal end as the 

 third pair of haemal nerves. 



(3) The Stomodaeal Nerves. — The stomodaeal nerves (Pis. 

 VIII and X, Figs. 3, 11, and 12, st.n}j were described by 

 Milne-Edwards and by Owen, and called the stomato-gastric 

 nerves. They arise from ganglionic swellings of the nerve 

 collar and extend along each side of the oesophagus, to 

 the proventriculus. Numerous branches are given off to the 

 oesophagus, and sometimes small branches are found arising 

 from the ganglionated bases of the nerves. At the sides of the 

 proventriculus the nerve breaks up into several branches which 

 ramify over the proventriculus, and on to the pyloric valve and 

 the beginning of the intestine. No branches could be traced 

 beyond the pyloric valve. 



Milne-Edwards described a ganglion upon each side of the 

 proventriculus, and two very fine branches of the stomato-gastric 

 nerves communicating with the median nerve of the heart, but 

 I have been unable to find either the ganglia or the cardiac 

 branches. 



