Te ee Ee aS ee ey SEs ee ae e n ETE eT NS Oe GS ae 
Sal fins grow 
1884. ] Batrachology in the years 1880-188}. 153 
the ova, the female lies with her anterior limbs extended laterally, 
and her hind limbs curved round the opening of the cloaca, ap- 
parently to assist in holding the eggs together. If disturbed she 
leaves the spot, and commences the operation elsewhere. The 
male deposits the spermatic liquid upon the eggs. The sperma- 
tozoa are very large, .75 millimetre in length, while those of Me- 
nopoma are only .25™™ and those of Rana temporaria .0o8™™ 
They are long slender filaments, pointed at both ends. The 
ova, as usual in Batrachia, have a light and dark-colored pole, but 
the dark portion, instead of being much smaller than the light 
one, as is frequent, is equal to it in size, so that the third segmen- 
tation furrow is equatorial. After this furrow is formed segmen- 
tation proceeds most rapidly at the light colored pole, which is 
always the lowest, and the dark area increases until the only 
light part left isa small area around the lower pole, and extend- 
ing upward from on one side. This white area then becomes sur- 
rounded by a furrow, and forms a prominence, the “ vitelline 
plug” of Ecker. Gradually the vitelline plug sinks into the mass 
of the egg, except a very small round spot, from which extend 
outwardly the rudimentary walls of the medullary folds. By the 
end of the fourth day these folds have spread anteriorly to the 
cephalic end, and the egg has now become elongated in the direc- 
ton of the medullary folds and their central groove. In about 
nine hours more the neural tube is enclosed, by this time the em- 
bryo has much increased in size and weight, and the entire sur- 
face is covered with cilia. A constriction next defines the head, 
and the optic lobes appear as oval prominences. The throat is 
next marked off, the proto-vertebre appear, branchial lobes are 
developed, and the anterior limbs indicated. The tail lengthens, 
and the balancers, so-called from their resemblance to the bal- 
ats of dipterous insects, appear between the eyes and branchial 
Obes. Active muscular movements next occur, the gills are de- 
fined, the pulsations of the heart are visible, and pigment cells are 
e Nerd. Most of the energy is now devoted to the growth of 
€ gills and balancers, and at the next stage the caudal and dor- 
actively. The balancers, held out so that they point 
d downwards, aid in keeping the head and branchiæ 
on the dirt at the bottom; they decrease as the anterior 
after Said and finally break off, about twenty-eight days 
33 ;, vitelline plug was formed. With the appearance of the 
utwards an 
mtd digit of the anterior limbs the lobes that will form the hind- 
