1891.] Embryology. 497 
embryo. A single anterior (to the six) slit appears, and others are 
also added behind the first-formed slits, ultimately the number of 
eight secondary gill-slits being formed. There is then a pause for a 
time in the formation of slits, and much later the tertiary slits appear 
behind on each side, and the number goes on increaeing during life. 
While these changes have been taking place in the gill region other 
important organs have been modified. The mouth has moved from 
its left lateral position to the mid-ventral line, and the oral hood with 
its buccal cirri has appeared. The V-shaped endostyle, at first high up 
on the right wall of the pharynx, moves as the primary gills move, from 
right to left, as far as the middle line, and at the same time the arms 
of the V become parallel, and the apex grows backwards between the 
gill-slits. The club-shaped gland, which communicates both with the 
cavity of the pharynx and the outer world, atrophies, and at the same 
time also the first primary slit. For this or other reasons the author 
believes the club-shaped gland to be a modified gill-slit,—the first of 
the secondary ones. 
In the theoretical part of the paper the asymmetry of the larva, 
the change of position of the endostyle, and the homologies of the 
club-shaped gland, are discussed. Interesting as this excursion is, 
it cannot be given here at all fully. It is assumed that the ancestral 
Amphioxus had a mouth opening in the mid-dorsal line, and that the 
growth forward of the notochord caused this to shift to the left side. 
At the same time the whole pharynx became twisted to the right, cor- 
responding to the movement of the mouth, so that the proper gill-slits of 
the left side were carried around to the right side. Consequently 
when these (the primary) appeared the gill-slits belonging to that side 
(right and secondary) were for a time retarded in development ; hence 
the asymmetry of the larva. 
Several sections deal with the homologies between the Ascidian tad- 
pole larva and Amphioxus, and the startling conclusion is reached that 
the intestine of the Ascidian is not homologous with the intestine of 
Amphioxus, but is to be compared to the club-shaped gland, and 
therefore represents the modified first right (secondary) gill-slit of 
Amphioxus. : f 
Development of the Pancreas in Batrachia.—The origin 
of the pancreas in both Urodeles and Anurans has been studied anew 
by Göppert.* In the embryos of both groups the pancreas arises by 
three evaginations from the intestine. One of these is from the 
dorsal surface; the other two from the sides, right and left. The 
3 Morph. Jahrbuch, XVII. Band, 1st Heft, 1891. 
