496 - The American Naturalist. [May, 
would in lapse of time culminate, till it had reached a proportion 
when obvious mechanical difficulties would more than balance the 
advantages resulting from superior size and vigor, and when, therefore, 
farther disproportion would be arrested. It may be added that the 
like disproportion of the sexes in the forms above enumerated fur- 
nishes not the slightest evidence of more intimate primordial affinity, 
for like causes would in each special case, such as this, produce like 
effects.  —THEODORE GILL. 
Errata of article on Chromatophores in fish embryos in February 
NATURALIST: Page 113, 9 lines from bottom, read oviparous for vivip- 
arous; page 114, 15 lines from top, read periblast for epiblast ; page 
116, 16 and 2ọ lines from top, read periblast for epiblast ; page 117, 
25 lines from top, read periblast for parablast ; page 118, 2 lines from 
bottom, read Hemirhamphus for Hemisbamphus.—C. H. EIGENMANN. 
EMBRYOLOGY. 
The Later Larval Development of Amphioxus.’ —Mr. 
Arthur Willey has published a most interesting account of the later 
stages of the larval Amphioxus. It is a continuation of a preceding 
paper by Professor Lankester and himself on the younger larva. In 
the first paper the larva, with its large mouth on the left side and the 
single row of gill-slits on the right, was described ; also the structure 
and position of the club-shaped gland and the endostyle were given, and 
the origin of the atrial folds, In the present account the author begins 
with a larva having fourteen primary gill-slits arrayed in a single ork 
and all on the right wall of the pharynx. Above these and on the same 
side is to be seen a thickened rod of endodermal tissue with six swell- 
ings. These later break through to form six secondary gill-slits, second 
to seventh inclusive. The atrium is still open in front. The posen 
primary gill-slits now begin seriatim to close and atrophy, beginning 
with the fourteenth and continuing until but eight remain. 
same time this primary row of gill-slits begins to move around the 
ventral surface to the opposite side of the larva (the left), "o : 
they assume their adult position. Meanwhile the secondary gill 
slits increase in number and size, and occupy the right side 
1 Edited by Dr. T. H. Morgan, Johns Hopkins University, Baltimore, Md. 
2 Quart. Jour. Micro. Sci., March, 1891. 
