THE 
AMERICAN NATURALIST 
VoL. XXV. JANUARY, 1891. 289. 
SOME RECENT PAPERS ON EARTHWORMS. 
BY J. S. KINGSLEY, 
Ls Oligochztous worms were long neglected, but within 
recent years the literature relating to them has extended to 
very considerable dimensions. It is the intention to present here 
an abstract of some of the work lately done on the group. The 
two papers’ by Dr. Wilson on the embryology of these forms 
may be considered together. The forms studied are called 
Lumbricus terrestris, L. communis, and L. Jætidus. 
The segmentation is unequal, but varies in its details in indi- 
vidual eggs of the same species. It results in the formation of a 
blastula, in which, at intervals, the blastoccel is in communication 
with the exterior by a cleavage pore. Some points of difference 
are shown between the species studied and that which formed the 
basis of Kleinenberg’s classic paper. 
Like Kleinenberg, Dr. Wilson finds that the “ primary meso- 
blasts” are differentiated before gastrulation as two large cells 
lying side by side, at first on the surface but later sinking into 
the blastoccel. Before this insinking they begin to bud off the 
mesoderm in the shape of two parallel rows of cells. During this 
process gastrulation takes place. The egg becomes flattened, 
and a differentiation of the cells of the two sides occurs, the upper 
1 Wilson, Edmund B. The Germ-Bands of Lumbricus. Journal of Morphology, 1., 
p. 183, I pl., 1887. : 
— The Embryology of the Earthworm ; Z. c., III., p. 387, 7 pls., 1889 [1890]. 
