SQUIRTS, POLYPS, AND JELLY-FISHES. 55 
adhering to the piles. Press gently with the finger— 
the animal contracts, and while contracting throws 
out a double jet of water from two chimney-pot open- 
ings situated on its surface. The animal is one of our 
commoner forms of sea-squirts, known to naturalists 
as Molgula Manhattensis. Through its pel- 
lucid outer tunic the color of the viscera 
can be indistinctly seen. This species 
also frequently attaches itself to floating 
sea-weed, and is then drifted in to shore; Moevra 
or it may be found attached to the nod- Ebene 
ding fronds which battle with the waves. 
The sea-squirts are in many ways interesting 
animals, especially since it has been shown that in 
their young condition they present many points 
of resemblance to the vertebrate or backboned 
animals. Thus, the larva of most species has a long 
tail, a rudimentary spinal column, and a long nerve- 
tract, terminating in a brain, which occupies the 
same relative position to the spinal column that the 
same tract does in the higher animals. Indeed, so 
similar is the larva of 
certain forms to atadpole 
as to carry with it a con- 
viction that the two can- 
not be very far removed 
from each other. But in the mature form of 
nearly all squirts the tail becomes absorbed, and 
with it disappears what there was to represent the 
spinal column, and also much of the nerve appa- 
ratus—a case of true degeneration. One of the 
chimney pot openings on Molgula conducts into 
LARVA OF TUNICATE. 
