Feb., 1921] Larval Colonies of Pectinatella 127 



all of the tissue of the other polyps of the colony has dis- 

 appeared. (Fig. 5). Then the mucus attachment elongates, 

 the animal drops off and dies. This change took place in the 

 specimens under observation in from three to four days after the 

 time of attaching. Here I transfer a few sentences from my notes. 

 Larval colonies of Pectinatella swept from around adults 

 July 3, all set July 4. Three colonies at the surface film, one 

 just at the middle of jar, four near the bottom. July 5, one 

 of the lower colonies gone. Two of the others have but two 

 colonies. Appear filled with algae. July 6, another gone. 

 Two colonies reduced to one polyp each. One has slipped on 

 the glass diagonally downward half an inch. July 7, out of the 

 eight colonies set on July 4, three are entirely gone, two have 

 one polyp apiece, three appear normal. July 8, one only — 

 near the bottom of jar. Planaria (Stenostomun) have been 

 seen to eat the polyps of Plumatella and I assume they may be 

 responsible for some of this disappearance.* 



If we assume that the larval colony develops from a single 

 fertilized egg, there is here a definite reversal of the growth 

 processes as an adaptation to external conditions. A slightly 

 similar type of reversal of growth occurs normally when the 

 tail of the transforming tadpole is absorbed. Possibly the 

 analogy is closer in the case of human disease when the fat and 

 muscle of the body is depleted, while the nervous system still 

 retains the large percentage of its tissue. The case in point, 

 however, is the resorption of an independent individual, prac- 

 tically cut off from the rest of the colony. 



In this particular case, if the explanation given is the true 

 one, we find a device for prolonging the life of Pectinatella in 

 the face of starvation, which should be of importance in the 

 distribution of the species. 



*It may even be that this gradual disappearance of the polyps of a colony is 

 due to their being eat^n, one at a time, by some carnivorous creature and to this 

 cause only. The regularity of reduction, however, would be in favor of the 

 hypothesis offered above. 



