142 BULLETIN OF THE 



they are found on the partitions immediately below the colony-wall. 

 Still later (Piute VI. Fig. 59, viu. rot., viu. rd.) we see them on the lower 

 portion of the partition, and linally (Fig. 5^), viu. rot., mu. ret.) they are 

 found attached to the sole, at some distance, it may be, from the 

 radial partition. 



The question arises at once, How do these changes of position take 

 place] Examination shows that the union between the ccelomic epi- 

 thelium and the cells of that portion of the funiculus which is attached 

 to the roof is very slight after the funiculus has passed to some distance 

 from the mother polyi)ide. Although occasionally I have seen the cells 

 of the fixed end closely applied to the ca^lomic epithelium, tlie only 

 comiection between the two is usually eflfected by means of ama^boid 

 cells (I'liite V. Figs. 46-48, cl. mi.). On cross sections of the fixed end 

 of the funiculus these cells (Fig. 49, cL vii.) are seen to surround it as 

 a loose layer, and in longitudinal sections some of the anueboid cells 

 are seen to be connected with the ccjehnnic epithelium. It is difticult to 

 determine the origin of these cells, but they have the position and 

 character of the cells of wliich.the funicidus was exclusively ct)mpo8ed 

 before the entrance into it of the ectodermal plug described by Ihaem. 

 The ouly explanation of the migration of the funiculus whicli occurs to 

 me has been suggested by tlie facts given above ; namely, that the 

 " migratory cells,"' by which the funiculus is attached to the ccelomic 

 epithelium, change their position, carrying with them the funiculus. 

 Remembering that the coenocoel is filled with a fluid in which the 

 funiculus floats, and that by the growth of the funiculus it is elongated 

 in proportion as the distance from its origin to the coccum increases, this 

 hypothesis does not seem improbable, altl)ough its truth can hardly be 

 tested by the study of preserved n)aterial. AVhen tlie funiculus has 

 reached its permanent position its attachment to the ccelomic epithe- 

 lium is more intimate. jNIeanwhile the end attached to the poly])ide 

 has become more and more attenuated (Plate IX. Fig. 11., fun.), until, 

 in the adult, I have usually been unable to discover any attachment. 

 In any case, it must certainly be broken Avhen the polypide begins 

 to degenerate. 



The migration downward of the ends of the muscles which are 

 attached to the partition is even more difficult of explanation. During 

 this migration their point of origin seems to be in the nniscularis of the 

 partition itself. Tlie fixed point of the muscle in the adult is probably 

 in the muscularis of the sole, since I have traced muscle fibres through 

 the ccelomic epithelium, and to the muscularis (Plate YI. Fig. 58, mu. 



