240 CALIFORNIA ACADEMY OF SCIENCES. 



In somites x and xi these hearts are connected by a 

 sub-dorsal vessel, which enters the tubular intestine prob- 

 ably in somite xi, and in somite ix passes directly into 

 the diverticulum of the tubular intestine. 



Except through these four hearts the two vascular 

 trunks do not directly connect in the central somites. 

 The ventral vessel emits one pair of secondary non-con- 

 necting vessels in each somite. A corresponding non- 

 connecting vessel (figs, i and 30) is also emitted by the 

 dorsal vessel in all the somites except ix, x and xi. In 

 the latter two somites they are replaced by hearts. This 

 secondary dorsal vessel is emitted in the posterior portion 

 of the somite, close to the septum. It runs at once straight 

 out through the body cavity, in almost right angles with the 

 dorsal vessel, until it strikes the body wall, where it 

 branches and forms a dermal system, especially developed 

 in the inferior part of the body, sending out ramifications 

 which extend along the longitudinal muscular layer below 

 the neural ganglion, but which do not connect or form 

 any sub-neural longitudinal system (fig. 30), all the 

 vessels being strictly transversal. In somites x and xi 

 these transversal vessels have been replaced by the hearts. 

 In somite ix one pair of lateral blood vessels pass from 

 the sub-dorsal vessel and the hearts through the diverticula 

 forming the lateral trunks (fig. i, Iv.), which extend for- 

 ward on either side of the worm to the peristomic region. 

 In each of somites v to viii, each one of these trunks 

 sends out one secondary vessel, which enters the septal 

 glands in the somite (figs, i and 2), and one vessel which 

 supplies the dermal and sub-dermal parts of the somite. 

 The main lateral trunk is branched in somite v or vi, 

 one branch going forward and upward, supplying the 

 prostomic and peristomic regions, while the other branch 

 furnishes the pharyngeal glands and muscles with the 



