114 The Development of Moina. | | February, 
observer of the general anatomical characteristics of his sub- 
jects, never examined the sternum of the adult G. americana, 
but only of what he considered the young. Yet we must con- 
clude this to have been the case, for had it been otherwise, we 
certainly should not have been left with only the above descrip- 
tion given without comment. 
In conclusion, I cannot refrain from alluding to a subject whieh 
it were better, perhaps, to leave untouched at this time. In 
making careful, detailed comparisons of the several sterna in my 
possession, in order to determine exactly in what particulars the 
two species differ, I could but notice that only two important 
conditions need be fulfilled to change the sternum of canadensis 
into that of americana. If the remaining portion of the keel in 
canadensis were thickened and hollowed, and the trachea should 
gradually increase in length, the arrangement seen in americana 
would certainly result, for the disposition of the trachea in. the 
latter species is exactly what would be produced by its forcing 
itself into the narrow limits of the keel. This may be simply an 
interesting relationship existing between the two structures, or it 
may have a deeper significance as the nature of the variations 
among the sterna of canadensis pointed out above, seems to 
imply. But considerations of this nature must be left for further 
investigation—until material of a determinative kind has been — 
obtained. 
EXPLANATION OF CUTS. 
Fic. 1.—Sternum and lower part of trachea of the sandhill crane, G. canadensis. 
The left wall of the sates has been removed, showing the trachea coiled cae 
inside. 
Fic. 2.—The same of the whooping crane, G. americana. The entire left side 
of the keel has been cut away to show the interior. The scapulars, clavicles 
and coracoids are in position in each. 
These drawings were very kindly made for the illustration of this article by my 
friend, Mr. C. L. Herrick. ‘They are about one-half natural size. 
:0: 
THE DEVELOPMENT OF MOINA?’ 
BY J. S. KINGSLEY. 
R. Carl Grobben having recently published one of the most 
complete accounts of the development of one of the Daph- 
nidæ which has yet appeared, an abstract of his piper may prove- 
of value to American naturalists. 
1 Die Entwickelungsgeschichte der Moina rectirostris. Arbiten aus ny Zoolog-. 
ischen Institute der — Wien. Tom. n, 2 heft, 1879, Pp- 66, pls. 7 
