Structure of Dolichoglossus Pusillus 
ALMA EVANS 
The animals were studied from serial sections cut in several planes. The stains 
used were carmine, hematoxylin and eosin. The hematoxylin seemed to show the 
tissues more clearly. A graphic reconstruction was attempted, but did not prove 
satisfactory because of the individual artificial foldings and contractions. The draw- 
ings were obtained by the use of a camera lucida. The general drawings, Figs. 1-9 
inclusive, are not filled in in great detail. The special drawings are shown at greater 
magnification with more of an attempt to show the actual condition. 
Dolichoglossus is a soft worm-like animal with ciliated surface. It is divided 
into three distinct regions: the probescis, a long club-shaped organ; the collar, a 
fold in the surface just behind the proboscis, and the trunk, a long cylindrical portion 
posterior to the collar. 
Dolichoglossus is a marine form living in sandy bays or sheltered places. Mucous 
glands in the surface epithelium secrete a sticky fluid which covers the body and to 
which tiny sand grains stick. The sand clinging to the mvcous coated surface forms 
a fragile temporary tube in which the animal is usually secluded. The animals in 
the living condition are bright orange or red but lose their color very soon after 
preservation in alcohol or formalin. 
The proboscis cavity extending the entire length of the organ is surrounded by a 
network of connective tissue supported by longitudinal bands of plain muscle. This 
cavity is supposed to communicate with the exterior by a very small opening, the pro- 
boscis pore, but this did not show in the specimens examined. The heart, proboscis 
gland and notochord are located in the posterior part of the proboscis. 
The collar contains the central nervous system, part of the notochord, the dorsal 
bload vessel, ventral and dorsal mesenteries, mouth opening and anterior part of the 
alimentary canal. 
The trunk contains the alimentary canal, dorsal and ventral blood vessels, dorsal 
and ventral nerves, the gill-slits, the reproductive bodies, dorsal and ventral mesen- 
teries and muscle bands. 
The nervous system consists of three parts: the central, located in the collar 
1egion, Fig. 5; the sub-epidermic network extending over the entire body just under 
the surface epithelium, Figs. 1-7; and the dorsal and ventral strands which are thick- 
enings of the sub-epidermic network extending throughout the trunk, Figs. 1 and 7. 
There is also quite a decided thickening of the sub-epidermic network at the base of 
the proboscis, Figs. 5, 6. 
The vascular system consists of two parts, the central and the peripheral. The 
central is made up of the heart, a thin-walled vesicle at the base of the proboscis 
just dorsal to the notochord, and connected with it the proboscis gland, a plexus of 
capillaries just anterior to the notochord. Fig. 5. The peripheral system is com- 
posed of a ventral and a dorsal vessel. The dorsal starts at the heart and continues 
just ventral of the dorsal nerve throughout the length of the body. Figs. 1, 5, 7. The 
ventral vessel extends from the posterior border of the collar to the anal end. It is 
connected with the dorsal vessel by a circular vessel in the posterior edge of the collar. 
The mouth is situated ventrally at the base of the proboscis, within the collar, 
