TAIL-EEGIOX OF POLISTOTREMA (fDELLOSTOMA) STOUTf. 31 G 
iiiyotomes of the great lateral or body-wall muscle than it is 
to the heart. 
Coucerniug’ the iuuervation of the musciili cordis caudalis, 
ill the 20 cm. and 85 mm. series there are four ventral spinal 
nerve rami that travel caudo-ventrad between the myotonies 
and tlie m. cordis caudal is and could innervate the in. cordis 
caudalis, but only from the third (counting* from cephalo- 
caudad) were any fibres seen going* to this muscle. The first 
of these nerves on the left side had its motor nucleus and its 
spinal ganglion considerably cephalad of the in. cordis caudalis 
or the caudal heart and slightly in advance of the forking* of 
the caudal artery and vein. Tt travelled gradually caudo- 
ventrad, and in the region of the anterior end of the heart it 
passed between the myotonies and the m. cordis caudalis, 
slightly nearer the former, which it innervated ; but abso- 
lutely no fibres were seen going* to the in. cordis caudalis. 
The motor nucleus and spinal ganglion of the second nerve 
was situated immediately dorsad of the passing* of the first 
ventral ramus between the myotomes and the m. cordis 
caudalis. Like the first nerve it travelled caudo-ventrad 
between the myotomes and the in. cordis caudalis in the 
region of the anterior end of the caudal heart, but did not 
innervate the m. cordis caudalis. The nucleus or the third 
motor root and the spinal ganglion was dorsad of the crossing 
of the second ventral ramus between the myotomes and the 
m. cordis caudalis, and at the posterior end of the heart the 
ventral ramus of the third spinal nerve passed between the 
myotomes and the ni. cordis caudalis, innervating both. In 
the case of the 85 mm. embryo the left caudal heart was in an 
embryonic condition at the point of innervation of the in. 
cordis caudalis by the ventral ramus of the third spinal nerve, 
consisting- only of the original left caudal vein and one 
mesenchymal cavity some distance dorsad of it. The nucleus 
of the fourth motor root and ganglion was situated imme- 
diately dorsad of the innervation of the m. cordis caudalis, and, 
like the other ventral rami, the fourth had a caudal ventral 
course between the myotomes and the extreme caudal end of 
