126 
ME. H. N. MOSELEY ON THE ANATOMY AND 
found sparingly present between the layers of the external circular muscular coat of 
that animal. The superficial muscles, both circular and longitudinal, are to be found 
all over the body-surface of Bipalium and Bhyncho demies, except on the under surface 
of the head of Bipalium , where they appear to be absent, being nevertheless well 
developed on its superior aspect. In the ambulacral line their arrangement is greatly 
modified ; but the description of this modification will be given when the general mus- 
cular structure of the ambulacral line is considered. Max Schultze, in describing 
Geoplana ( loc . cit. p. 35), says that the longitudinal muscles are external as in other 
Turbellarians ; but as he only had one specimen to work at, and apparently did not 
examine that by means of sections, it is possible that a delicate external circular coat 
w 7 as overlooked. 
Deep Muscular System. — A broad zone, already described, occupied by loose radiating 
muscular fibres and various skin-organs, intervenes between the superficial and deep 
muscular systems in Bipalium and Bhynchodemus. Internally to this zone the whole of 
the body may be regarded as made up of a dense mass of muscular fibres, in which 
are hollowed out the digestive tract, water-vascular canals, and space for the generative 
system, and the interstices of which are more or less filled up with glandular matter 
and connective tissue. The muscular mass consists of fibres which in their general 
arrangement may be described as longitudinal, circular, and radiating. 
In a transverse section of Bipalium or Bhynchodemus , longitudinal fibres are seen in 
cross section, dotted all over the central mass of the body, but in certain regions they 
are much larger and more numerous than in others. Thus they form a conspicuous 
zone on the periphery of the central gastro-intestinal tube near the commencement of 
the intestinal diverticula, as may be seen in Plate X. fig. 5 ; and in this zone the fibres 
are especially stout and closely aggregated infero-laterally, where they appear in section 
as irregular masses separated from one another by fibres of the radiating system. A 
similar aggregation of fibres forms a pair of longitudinal bands which run the entire 
length of the body, one on each side of the ambulacral line. A further special develop- 
ment of longitudinal fibres is constituted by a group of small fibres around the oviduct. 
Over the remainder of the central body-mass the longitudinal fibres are scattered pretty 
evenly; they are entirely absent in the zone of loose radiating fibres intervening 
between the central muscular mass and the skin-muscles, and in the main water-vascular 
trunks. 
Circular and radiating Muscular Fibres. — There is no separate and distinct circular 
muscular layer in the inner muscular mass, though fibres more or less circular in their 
direction are dispersed all over the body-mass ; an especial number of these is to be 
found at the lateral regions of the body, just externally to the extremities of the intes- 
tinal diverticula. In Bhynchodemus the circular fibres in the corresponding region are 
more highly developed, and form a tolerably well-defined layer, lying just externally to 
the internal mass of longitudinal fibres, as may be seen from Plate X. fig. 7 and Plate 
XI. fig. 2 ; and this layer appears to be homologous with that which exists in Lepto - 
