730 The American Naturalist. | August, 
EMBRYOLOGY. 
Some Activities of Living Eggs.—R. V. Erlanger’ has pub- 
lished a brief account of the fertilization and thelfirst cleavage stages of 
the eggs of several small Nematodes found in decaying earthworms; 
chietly Rhabdites dolichura and R. pellio. 
Some of the phenomena seen in the living eggs seem of special inter- 
est as adding to our knowledge of the ameeboid power of egg protoplasm 
and at the same time furnish a welcome supplement to the results 
obtained upon the same and other nematode eggs by aid of reagents. 
The sperm removed from the receptacle exhibits active amceboid 
movements at its conical end—the pseudopodia arise from folds that 
branch and anastomose and are capable of sudden, sharp bending move- 
ments at the free ends. 
The egg shows active streaming currents in the protoplasm and 
amceboid movements at the end where the polar bodies are forming. 
_ The egg nucleus moves rapidly towards the centre of the egg, appar 
ently owing to the energetic streaming movements of the egg proto- 
plasm, seen chiefly at the polar body end of the egg. This same end 
shows marked ameeboid changes of outline that result in a deep furrow 
marking off from the larger end with the sperm nucleus a smaller blasto- 
mere-like end of the egg with the egg nucleus. The movement of the 
egg nucleus continues till it reaches the sperm nucleus lying at the pole 
opposite to the polar bodies, : 
A centrosphere appears and divides to form a spindle. The two nuclei 
coming together are flattened against one another and look like vesicles, 
each with a nucleolus. The spindle lies in the plane between the two 
nuclei and accompanies them as they slowly move toward the centre of 
the egg; the migration is accompanied by slow streaming throughout the 
entire egg and an obliteration of the external furrow that had marked 
off the egg into blastomere-like portions. In this migration toward 
the centre, the two nuclei stagger and turn somewhat, without losmg 
their mutual relations of position. 
At the centre of the egg the spindle assumes a position 
with the long axis of the egg and the two nuclei elongate para 
astral rays become prominent from the ends of the spindle. ; 
1 Edited by E. A. Andrews, Baltimore, Md., to whom abstracts, reviews s 
preliminary notes may be sent, es 
? Biologisches Centralblatt, XVII. No. 4, p. 152-160 and No. 9, P- 339-346: 
to coincide 
Jlel toit ; 
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