OIRCULATORY APPARATUS OF THE NEMERTEA. 9 
Along the whole length of the body there are two muscular 
coats within the basal membrane, a circular layer and a longi- 
tudinal one. In the head and in the esophageal region a third 
layer occurs between the outer (circular) layer and the basal 
membrane, viz. a layer of isolated bundles of longitudinal mus- 
cular fibres. The bundles are separated from one another 
by hyaline basal tissue. In the cesophageal region a number 
of fibres of the circular muscular coat of the proboscidian 
sheath direct themselves round the esophagus. Further back- 
wards they increase in number, whilst they diminish beneath 
the proboscidian sheath. At last there is no muscular fibre 
between proboscidian sheath and intestine, and a little more 
backwards the process repeats itself in a reverse manner, so 
that the proboscidian sheath is again surrounded by its circular 
muscle, and no more fibres go round the intestine. Further, 
here and there in the head and the post cerebral region more 
transverse bands of fibres appear, which, however, are of 
secondary importance. 
The brain is situated outside of the two characteristic mus- 
cular coats, though the above-mentioned layers of isolated 
longitudinal bundles are situated externally to the brain. 
Also the two lateral nerves lie in the cesophageal region 
outside of the two muscular coats, penetrate a little further 
backwards into the circular coat, and gradually come to lie 
between the longitudinal muscular fibres, moving still a little 
further again outwards, remaining, however, between the two 
layers. 
The intestine has no diverticula. 
Of the vascular system I will treat afterwards. In truth, 
in regard to this system, I can correct McIntosh only in one 
respect, viz. in regard to the mutual communication of the 
six vascular trunks. 
The mouth is situated behind the ganglia. 
The proboscis has no stylet. 
The head has no deep lateral longitudinal furrows. 
Posterior lobes (brain respirators, cephalic sacs) are ab- 
sent, 
