VASCULAR SYSTEM OF PHERETIMA 39] 
6. SUMMARY. 
1. The typical arrangement of the blood-system in Phere- 
tima occurs in the region of the body behind the fourteenth 
segment, the first fourteen segments forming the cephalized 
region. The main longitudinal trunks are the same as in 
Lumbricus, except that the lateral neurals are absent as 
in Allolobophora. The dorsal vessel receives two pairs 
of dorso-intestinals and one pair of commissurals in each 
segment behind the cephalized region. 
2. The intestinal blood-plexus is both an external and an 
internal one, and three regions can easily be distinguished. 
The first is internal, and extends from the fourteenth to the 
twenty-sixth segment; the second is both external and 
internal, is co existent with the typhlosole, and extends over 
the larger part of the gut; and the third is only external, and 
is confined to the rectal or post-typhlosolar part of the gut 
(last twenty-three to twenty-six segments). 
3. The commissural vessel of Pheretima is a compound 
vessel, and represents both the ‘ dorso-sous-nervien’ of 
Lumbricus and the intestino-tegumentary of Megascolex. 
The capillaries of the integument are not like those of Lum- 
bricus but like those of Moniligaster, and there is 
a close * parallelism ’ between an ‘ artery ’ and a ‘ vein’ in the 
body-wall, in which the two pass into each other through 
a number of capillary loops. 
4. There are four pairs of ‘ hearts ’ which connect the dorsal 
with the ventral vessel, and five pairs which supply blood 
directly to the various organs in the cephalized region. There 
are two pairs of non-contractile ‘ anterior loops’ connecting 
the lateral oesophageals with the supra-intestinals, these loops 
being the counterpart of the connexions of the lateral oesopha- 
geals with the dorsal and the parietal in the tenth and twelfth 
segments respectively of Lumbricus. ‘The subneural 
vessel is absent in the first fourteen segments, and is con- 
tinuous with the lateral oesophageals of the anterior region. 
5. As regards the course of circulation of the blood, the chief 
