Pomona College, Claremont, California 29 
and opens directly into the straight alimentary canal. The latter is a straight tube 
extending from the mouth opening to the anus. Figs. 5, 1, 7, 9. 
The alimentary canal in the anterior part of the collar gives off a diverticulum, 
which grows forward and supports the proboscis. Because this diverticulum has the 
vacuolated appearance of the notochordal tissue of higher animals, it has been re- 
garded as a notochord. It is largest at the base of the proboscis immediately anterior 
to the heart. Figs. 5, 6. 
The paired gill-slits occupy the region just posterior to the collar. ‘They are 
arranged in two longitudinal grooves in the dorsal wall. The number increases 
throughout life, new slits appearing just behind those already in place. I found 
about twenty-five to be the average number, while particular individuals had as low 
as eighteen and twenty and as high as thirty and thirty-one. The gills are formed 
in the shape of a U. A skeletal rod or gill bar separates the gills from each other. 
The gills are supplied with blood from the dorsal vessel. Figs. 3, 7, 8. 
The sexes are distinct. The ovaries and testes are saccular organs arranged in 
a row along the gill and succeeding region. The sacs in other genera, for example 
Balanoglossus as described by Shipley, open directly on to the epidermis. I have been 
unable to see these openings in my preparations. Fig. 8 shows the position of the 
ovaries in the female; the testes in the male are in a similar location. 
The surface epithelium is modified ciliated columnar, varying slightly in thick- 
ness, size of nuclei and size and shape of cell according to location. Figs. 13, 14, 15. 
The epithelium forming the gills and intestine is also modified ciliated columnar. 
That of the gills having short narrow cells and small nuclei, and that of the intestine 
having longer thicker cells and large nuclei. Figs. 11, 10. 
The connective tissue surrounding the proboscis cavity is of a peculiar arrange- 
ment. The connective tissue itself consists of fine strands losely interwoven, but 
arranged in a definite manner. The strands form a fine network which gives a beauti- 
ful lacy appearance. Small round nuclei are quite numerous in connection with the 
strands. Longitudinal bands of plain muscle are very conspicuous in the connective 
tissue. These muscle bands are probably used in altering the size and shape of the 
proboscis. Figs. 4, 20, 21. 
The nervous tissue consists of many fibers thickly interwoven. There are a few 
small nuclei scattered about among the fibers. Figs. 12, 13. 
The muscle is unstriated. The fibers are very long in some places, shorter in 
others and always quite distinct. 
(Contribution from the Zoological Laboratory of Pomona College) 
REFERENCES 
Assheton, Richard 1918 
A new species of Dolichoglossus. Zool. Anz. Bd. 33, p. 517-520. 
Delage and Herouard 1898 
Traité De Zoologie concréte Vol. 8. Les Procordés. Balanoglossus. 
Eneyclopedia Britainica Balanoglossus. 
Shipley, Arthur E. 1893 
Zoology of the Invertebrata. Balanoglossus. 
