86 INVERTEBRATE ZOOLOGY 
The different individuals of a colony have arisen by a process 
of budding from the individuals below them in the colony. 
The oldest individuals are thus those nearest the base of the 
colony, the basal one being the progenitor of the entire colony. 
This is also the only individual which has not come into exist- 
ence by a process of budding; it began its life as a free- 
swimming larva which was hatched from an egg. 
The zoecium. Mount a small portion of the colony containing 
two or three branches on a slide under a cover-glass. 
Exercise 1. Draw a large and accurate outline of the zoccia, 
leaving out the polypides. Observe very carefully the 
boundaries of the zocwcia and their relations to one 
another. 
The polypide. Study a number of polypides, both retracted 
and extended. The forward end of the polypide consists of a 
circular ridge, called the lophophore, which bears a row of long 
ciliated tentacles. In the midst of the circle is the mouth. The 
tentacles are very vibratile and serve as respiratory as well as 
prehensile organs. It will be seen that the lophophore can be 
entirely withdrawn within the zocecium. 
The digestive system. The mouth opens into the pharynx, 
which leads into the esophagus. This opens into a large sac- 
like stomach, the lower portion of which is lengthened into a 
long pouch. From the upper end of the stomach, near the base 
of the cesophagus, the short intestine leaves it and passes to the 
thick-walled rectum. This leads to the anus, which is situated 
just outside the lophophore near the mouth. The digestive tract 
has thus the shape of the letter V, the point of which is formed 
by the stomach pouch. Passing from the stomach pouch to the 
lower end of the body is a broad mesenteric strand called the 
funiculus. In order to study the digestive tract satisfactorily, 
a polypide should be found in which both arms of the V come 
into view. 
