rv 
106 E. RAY LANKESTER, ON THE 
vessel itself, broken up into a capillary network mvesting the 
pharynx), they assume a more or less doubly conical form, 
and have been called by authors on the subject “ hearts” (see 
Part TPL SY Ey fig.) 
When the nervous cord extending along the ventral in- 
terior surface is dissected away from its attaching branches, 
and its inferior surface is examined, a delicate vessel, capable, 
however, of much expansion, is seen closely attached to it, 
sending out branches with the nerve-branches, and, in fact, 
following the ganglionic cord and its branches throughout 
the worm (figs. 1, 2, 3,4). It forms a capillary plexus at 
the cephalic and at the caudal extremities, thereby commu- 
nicating with the dorsal and sub- intestinal trunks ; ; this is, 
then, the main trunk of the cutaneous system, the singleventral 
vessel representing the two longitudinal lateral vessels met with 
in some other Annelida. The rest of the cutaneous system 
(figs. 1, 2, 3, e) of vessels is seen in the innumerable 
ramifications and delicate networks visible on the inner 
surface of the perivisceral cavity, which form one of the main 
objects of beauty attracting the eye when an earthworm is 
opened for dissection. There is no special superficial cuta- 
neous circulation, that is to say, disposed near the external 
surface ; a few vessels penetrate the muscular layers of the 
integument and give off numerous delicate branches, which 
are occasionally seen in the pigmentary layer ; but there is no 
great cutaneous plexus, as, in fact, may be partly seen by the 
completely colourless aspect of the posterior three fourths of 
any worm’s body ; in fact, the integument of the earthworm 
has a remarkably small true cutaneous circulation, being, 
such as it is, merely adapted to perform the general offices of 
a vascular fluid. It is upon the interior superficies of the 
integuments that a plexus exists, belonging to the cutaneous 
system of M. Milne Edwards, which, perhaps, it were better 
to call peripheral. This plexus is supplied in each segment 
by a branch on either side from the ventral or sub- ganglionic 
vessel; it is also connected in each segment (the seven cepha- 
lic segments are exceptional) with the sub-intestinal vessel 
by a special branch on either side, and with the dorsal vessel 
by large vessels, given off on either side, closely connected 
with the diaphtasmatic muscle, and sending branches else- 
where also. These latter vessels, or their representatives in 
other Annclids, are what M. Milne Edwards calls the datero- 
dorsal vessels. Thus, then, we see a general connection 
* A somewhat serious error has been unaccountably made in the figure 
referred to. ‘There should, of course, be but oze pair of “hearts” in each 
? 2 
segment. 
