530 
Batrour and Parker first observed, described, and figured the 
cleavage of the egg of Lepidosteus. Their conception of its character 
is concisely stated in these words: “We have observed several stages 
in the segmentation, which show that it is complete, but that it 
approaches the meroblastic type more nearly than in the case of any 
other known holoblastic ovum. 
“Our earliest stage showed a vertical furrow at the upper or 
animal pole, extending through about one-fifth of the circumference, 
and in a slightly later stage we found a second similar furrow at 
right angles to the first. We have not been fortunate enough to 
observe the next phases of the segmentation, but on the second day 
after impregnation, the animal pole is completely divided into small 
segments, which form a disc, homologous to the blastoderm of mero- 
blastic ova; while the vegetative pole, which subsequently forms a 
large yolk-sac, is divided by a few vertical furrows, four of which 
nearly meet at the pole opposite the blastoderm. The majority of 
the vertical furrows extend only a short way from the edge of the 
small spheres, and are partially intercepted by imperfect equatorial 
furrows’. 
BEARD next described the cleavage phases stating that “The 
segmentation is very unequal, but in a sense complete. Eight furrows 
can be traced to the center of the Jower pole. The attempt to segment 
the lower hemisphere is, however, soon given up, none of the eight 
furrows penetrate very deeply into the yolk, and none reach the 
center by a long way. They are only superficial furrows”. 
DEAN more recently gives a description and delineation of the 
successive cleavages and concludes that the egg is meroblastic. In 
the detailed accounts of the successive meridional and _ vertical 
cleavages (p. 16—19) the author explicitly states, iterates and 
reiterates that the grooves extend no further than the margin of the 
blastodisc. 
Bearp still later affirms his former statement and adds these 
words: “If DEAN were correct, the segmentation in Lepidosteus would 
be to all ixtents and purposes that of Scyllium, whereas if the view 
Batrour and PARKER, and I took of it, be the right one, it would 
form a link between that of a frog or newt on the one hand and 
that of a skate or dog-fish on the other. 
“This being so, the question of fact becomes of some importance. 
Dean has certainly had good opportunities for making sure of the 
point and my own have been equally good. So far as can be gathered 
from Dean’s statement and from my own abundant material of this 
