1892.] Zoology. 1037 
ZOOLOGY. 
On Nectonema agile Verrill.'—Warp, H. B.—Dr. Ward’s paper 
upon this curious nematode has been awaited with considerable inter- 
est by all who heard his preliminary paper given before the Society of 
American Morphologists last winter, and, in justice to Dr. Ward and 
Prof. Mark, in whose laboratory the work was done, it must be said 
the paper is up to ourexpectations. Many curious thread-worms have 
been described heretofore, but helminthologists have generally been 
able to give homologies in other species for all the organs mentioned. 
Verrill’s curious Nectonema, however, is a worm which possesses cer- 
tain structures which are totally foreign to other nematodes. 
According to Ward, Nectonema is a long (50-200 mm.), slender and 
exceedingly active round worm, found swimming at the surface of the 
sea with a rapid, undulatory motion. The anterior portion of the body 
is semi-transparent, and internally an anterior chamber is divided from 
the general body cavity by a partition which is concave anteriorly. 
This anterior chamber, together with its contents, is the most interest- 
ing part of the animal in question, for it is a structure which we cannot 
at present homologize with any organ of other nematodes. It is tra- 
versed by the rudimentary wsophagus, and contains ventrally the 
brain, while the dorsal space is occupied by four large conical cells 
which send processes down into the nervous matter of the brain. These 
cells are looked upon by Briiger as gland cells, but Ward supports the 
view that they are ganglion cells, which were situated on the surface of 
the brain, have become enormously large, and have extended up above 
the brain into the lumen of the anterior chamber. At first thought 
this supposition would seem rather far fetched, but, curiously enough, 
Ward has shown that there are in the brain five pairs of large ganglion 
cells which are quite constant in their position and which resemble 
these two pairs of dorsal cells in certain respects ; the fifth pair of cells 
is only half in the brain and half projecting above it, thus apparently 
forming the first stage in the migratt hich the dorsal cells h lready 
accomplished. . 
The digestive tract is quite rudimentary, and, as Ward states, points 
directly to the view that Nectonema is, in all probability, a parasite 
during the earlier part of its life. 
— Mus. Comp. Anat., Cambridge. 1892. Vol. xxiii, p. 135-188, with 8 
