Katharine Foot and E. C. Strobell s¢ | pesl 
chromosomes can scarcely be wholly accounted for on the ground of 
contraction alone. The eccentric chromosome of Photo. 39 also shows a 
relative inequality in size—the inconsistency of its size in relation to the 
other chromosomes is even greater than that mentioned above for the 
large cross-shaped bivalent of Photos. 5 and 6, Plate II. These remark- 
able inconsistencies can be fully appreciated only by more exhaustive 
work on each form, and we have not yet been able to undertake this in 
Anasa. In our selection of cells to illustrate the phenomenon of the 
lagging chromosome we have made no special effort to demonstrate indi- 
vidual variations, but we hope to continue our study of Anasa tristis with 
the view of giving more exact data on this point. Individual variations, 
however, can scarcely be called upon to explain away the evidence we 
have given to demonstrate the division of the lagging chromosome of the 
second spindle. 
These variations, which cannot be wholly explained by technique or 
contraction, offer a tempting invitation to premature speculations. The 
variations we find not only in the size of individual groups of the same 
stage but between members of the same group, and also variation in the 
individual form and in the grouping of the chromosomes seem to offer 
quite as plausible a field for speculation as to the relation of these varia- 
tions to the adult individual, as much of the evidence we have been asked 
to consider as a morphological explanation of other vital phenomena. 
We do not underrate the fact that the phenomena of Idiochromosomes 
observed by Miss Stevens, 05, and Wilson, 05, present a strong case in 
favor of the theory of the conjugation of paternal and maternal chromo- 
somes, but in this paper our discussion of this theory is clearly limited to 
an attempt to point out its bearing on the phenomena as we find them in 
Anasa tristis. 
New York, May, 1907. 
BIBLIOGRAPHY. 
Buenton, E. and Poporr, N., 05.—La Spermatogénése du Lombric terrestre. 
Arch. Zool. Exper. et gen. Vol. III. 
CALKINS, G. N., 95.—The Spermatogenesis of Lumbricus. Journ. Morph., 
Vol. XI. 
Foor AND STROBELL, 05.—Prophases and Metaphase of the first Maturation 
Spindle of Allolobophora fctida. The Amer. Journ. Anat., Vol. IV, 
No: 2. 
o7.—The “Accessory Chromosome” of Anasa tristis. Bio. Bull. 
WOE DE 
