216 STUDIES IN GENERAL PHYSIOLOGY 
Hydroid, Hydra, should conduct itself, so far as known, as 
a strictly “polarized” animal, might render it still more 
probable that heteromorphosis is simply a characteristic of 
“colony-forming’’ Hydrozoa. To settle this question I made 
experiments upon Ciona in- 
testinalis, a solitary Ascidian. 
The Ascidians, as is well 
known, stand near the verte- 
brates in the animal scale. 
In Fig. 54 is shown in 
almost natural size the exter- 
Queen ----- ry 
B) 
C/ 
FIG. 54 FIG. 55 FIG. 56 
nal form of a Ciona intestinalis. ais the oral opening, b 
the excretory opening, ¢ the foot, which, like the foot of the 
Hydrozoa, attaches the animal to the surface of solid bodies. 
At the outer edge of both tubes are situated the ocelle, 
which are just visible to the naked eye (Fig. 55). The fol- 
lowing experiments deal with the formation of these ocelle. 
If the animal behaved like a purely “polarized animal,” such 
as Cerianthus, then, when a lateral incision cba (Fig. 56) is 
made into it, ocellee should be formed only along the lower 
cut edge be, just as the tentacles are formed only along the 
lower cut edge of Cerianthus. But the opposite occurs in 
Ciona. After a short time ocelle (indicated by points in the 
drawing) are formed along both edges of the wound (ab and 
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