126 The Ohio Journal of Science [Vol. XXI, No. 4, 



The process of attaching is a very rapid one and has been 

 observed a number of times. A specimen will be swimming 

 and when possible striking the top of its float against some solid 

 body. The side of the jar can be used in default of anything 

 which can be struck more directly from beneath. Those 

 observed were seen to fix the apex of the float to the glass, to 

 shrink to as little as one-fourth of their swimming length and 

 show in the center, between the polyps, a mass of orange- 

 colored yolk. (Fig. 3). The epithelium of the place of attach- 

 ment is sticky, so if the colony is scraped off at once it will 

 stick to the knife. There are, in my opinion, as many sticky 

 points at the top of the float as there are polyps in the colony, 

 since attachment can be made a little off from the exact center 

 of the float. 



The larger portion of the float, in addition to being ciliated 

 on the outside, possesses delicate bands of tissue in its wall 

 which, when the colony attaches must serve to compress the 

 contents of the cyst and to bring the yolk into the central 

 region between the polyps. The liquid material which is 

 contained in the cyst as it swims, shows very little of the orange 

 color which characterizes the yolk of the attached colony. 

 It is possible that this liquid content is a salty solution, in which 

 case vitellin would be dissolved in it. If then, when the colony 

 attached, the salt was taken up by the cells of the organisms, 

 the dissolved yolk material would at once appear, as yolk is 

 insoluble in water. There is, however, in preserved free 

 colonies some solid yolk, as has been demonstrated by sec- 

 tioning, so that the fact that none is visible may be due to the 

 central position it holds. The rapid contraction of the walls 

 of the cyst may force the yolk into the center between the 

 polyps where it is most conspicuous. (Fig. 2). 



The colonies, after attachment to the side of the jar, find no 

 adequate supply of food. Since they starve to death in spite 

 of the fact that the alimentary canals of many of them showed 

 that they were filled with one-celled algae. I assume Pectinatella 

 uses animal food. For the colonies exist and differentiate 

 only as long as there is a yolk supply. (Fig. 4). Some of 

 them, at least, then retrogress in an interesting way. Instead 

 of all the polyps starving at once they are reduced successively 

 from four, or the normal number, to three, to two, to one. 

 The latest persisting polyp appears normal and healthy until'- 



