MUSEUM OF COMPARATIVE ZOÖLOGY, 39 
That the nutritive matter in the cwlomic cells is supplied to the 
young bud is what we should expect, since the cells of the bud, being 
most actively engaged in growth, will require most nutriment. The 
actively dividing cells of the outer layer of the bud are thick and cuboid, 
and are rarely so highly vacuolated as the more passive ones of the body 
wall; yet occasionally one finds one or two huge cells in this layer full 
of vacuoles, which contain highly refractive bodies. In most cases these 
cells send out processes into the colom, and in a few instances I have 
seen them united with similar processes from cells on distant parts 
of the body wall. This remarkable phenomenon, shown in Figure 54 
(Plate VI.), may possibly signify that cells of the cœlomic epithelium at 
times directly communicate with those of the outer layer of the bud to 
supply it with nourishment. Nutrition of the bud is also probably 
effected through the presence of large reticulated cells at the angle 
between the bud and the body wall, A condition like that shown in 
Figure 56, cl. ret., is very common, 
Every author from Dumortier et van Beneden to Braem, who has 
studied the origin of the polypide in Paludicella, has mentioned the 
presence of highly refractive bodies in the alimentary tract at the time of 
its formation. “These are very striking in some living specimens, and 
in whole animals after killing. I have found that this highly refractive 
substance in the bud is exceedingly variable in amount and position, 
and that sometimes it is apparently absent. When present, it usually 
occupies the lumen of the forming alimentary canal ; but, as sections 
show, it is often located in large vacuoles in the future digestive cells 
of the alimentary tract. It seems highly probable that, as Braem sug- 
gests, this is nutritive substance, and it has doubtless come from the 
body cavity through the agency not only of the outer layer of the bud, 
but also of other parts of the coolomic epithelium. 
I am inclined to interpret the phenomenon of cells filled with nutri- 
tive material as an adaptation to the peculiar conditions of Paludicella, 
in which the individuals are early separated from one another, except 
for the communication plate, through which at best fluids can pass only 
slowly, and in which a rapid growth of the body wall to produce the 
poly pide 3 place periodically. The mesodermal cells rapidly absorb 
the nutritive fluids of the body cavity and store them in their substance 
before the formation of the communication plate, and give them out 
again during the period of the polypide’s most rapid growth chiefly to 
this part of the individual. This hypothesis has been mainly derived 
from considering the fact of the great development of the reticulated 
