166 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Amphioxus , being led, by the position of the endostyle, to conclusions 
diametrically opposed to those of van Beneden and Julin. 
His chief results are to be thus summarized : — 
(1) The first four primary stigmata of Ciona intestinalis are deve- 
loped from one primitive gill-slit. 
(2) Three pairs of gill-slits, in the form of six primary stigmata, 
are represented in Ciona and other simple Ascidians. Jn Ciona the 
innumerable branchial stigmata of the adult are derived by subdivision 
from these six primary stigmata, and not by new perforations. 
(3) The endostyle of Ciona is at first quite anterior in position, 
lying in front of the mouth, with its primary long axis at right angles 
to its definitive long axis. 
(4) The cavity in the fixing stolon is the praeoral or anterior body- 
cavity, and contains loose mesoderm cells derived from the two lateral 
mesodermic bands. 
(5) This stolon, which is at first quite anterior, has its position 
reversed by the rotation of the body of the Ascidian through a right 
angle. 
(6) The walls of the atrial cavities of Ascidians are essentially ecto- 
dermic, there being no difference in this respect between the somatic 
and visceral walls. 
(7) The pericardium of Ascidians arises from the endoderm of the 
branchial sac, and the heart has no endothelium. 
(8) The heart of Ciona arises by the splitting apart of the two layers 
of the septum which primarily divided the pericardium into two halves. 
(9) On the whole, the development of Clavelina , as compared with 
that of Ciona , is greatly modified in the direction of abbreviation. With 
this may be correlated the development of the former in the peribranchial 
cavity, and the possession by the eggs of much more yolk than is found 
in those of Ciona. 
The history and structure of the heart of Tunicates leads the author 
to accept the view of Van Beneden and Julin that it is a special organ 
in the group of Urochorda, and that it is not homologous with the heart 
of Vertebrates. 
The author gives the following scheme to show his view of the rela- 
tions of the Protochorda : — 
Mouth ventral. 
No endostyle. 
Mouth dorsal. 
Endostyle. 
Cephalodiscus. 
Sessile. 
U-shaped alimen- 
tary canal. 
One pair of gill- 
slits. 
Buds. 
N / 
Balanoglossus. Ascidians. Amphioxus. 
Free. Sessile. Free. 
Straight alimentary U-shaped alimen- Straight canal, 
canal. tary canal. Many gill-slits. 
Many gill-slits. Three pairs of gill- No buds. 
No buds. slits. 
Buds. 
