€ Cit ) 
which one is recurrent (recurrent br. fig. VI) and leaves the septum 
to go over into the skin at 1 V and 2 V. fig. V. 
The internal branch can be followed up to the vena lateralis (VZ, 
fig. IV) and then goes over in a loose plexus. On its way to the vena 
lateralis the internal branch gives off several filaments, which reach 
the skin through the intermyotomal septum 3 V—6V fig. IV and V. 
Before passing over into the skin these filaments form a loose plexus 
covering the most ventral part of the myotome. 
The roots and mainbranches of the spinal nerve have a submyotomal 
position and are not bound in their course by the form of the 
myotome; these branches on the contrary, which go over into the 
septum to reach the skin, are in their course fixed by the form of 
the myotome. The final course of the branches in the corium was 
not traced out with enough accuracy to give results here. 
The descriptions given in this note only apply to that region of 
the trunk which is situated between the thoracie and first dorsal fin. 
Conclusions : 
I. One single spinal nerve only innervates one single myotome 
and the intermyotomal tissue through which the nerves pass. 
IL. The roots and mainbranches of the spinal nerve have a sub- 
myotomal position; the branches never perforate a myotome, but 
run always in the intermyotomal septum to the skin. In general 
they are to be found between the perimysium and the intermyotomal 
septum. 
III. The spinal nerve shows a primary division into three parts, a 
posterior, lateral and anterior division in agreement with the diffe- 
rentation of the myotome in a dorsal, lateral and ventral part. 
IV. All larger branches are mixed nerves containing elements of 
the anterior and posterior roots. 5 
Mathematics. — “On linear systems of algebraic plane curves”. 
By Prof. JAN pe Vries. 
$ 1. The points of contact of the tangents out of a point O to 
the curves ce" of a pencil lie on a curve *—! which I shall call the 
tangential curve of QO. It is a special case of a curve indicated by 
Cremona’). By Emm Werr?), Guccta*) and W. Bouwman‘) it has 
been applied when proving the properties of pencils and nets. 
1) Cremona—Currze, Einleitung in eine geometrische Theorie der ebenen Curven 
(1865) p. 119. 
°) Sitzungsberichte der Akademie in Wien, LXI, 82. 
5) Rendiconti del Circolo matematico di Palermo (1895), IX, 1. 
4) Nieuw Archief voor Wiskunde (1900), IV, 258. 
