CONCERNING "LARVAL" COLONIES OF PECTINATELLA. 



Stephen R. Williams, 

 Miami University. 



During several summer sessions of the Lake Laboratory of 

 the Ohio State University, as occasion offered, the sexual 

 reproduction of the Bryzoan Pectinatella has been kept under 

 observation. 



As is well known, Pectinatella grows in large submerged 

 masses attached to any artificial support. The thickened 

 cuticle which makes the skeleton of Bryozoans is in this case a 

 gelatinous mass with the polyps distributed in irregular patterns 

 over the surface. When the colony reproduces sexually the 

 fertilized egg is retained for a time in the superficial portions 

 of the gelatin. There it develops what Parker and Haswell, 

 Vol. I, p. 325, call "a ciliated hollow cyst from which the 

 colony is derived by gemmation." 



The individual polyps connected with this cyst are not 

 especially embryonic and can hardly be distinguished from 

 polyps dissected out from an adult colony. According to the 

 Cambridge Natural History, Vol. II, p. 512, "The peculiarity 

 of the Phylactolaematous larva may be explained by assuming 

 that it becomes a zooecium while it is still free-swimming. 

 Thus the larva of Plumatella develops one or sometimes two 

 polypides which actually reach maturity before fixation takes 

 place. That of Cristatella develops from two to twenty 

 polypides or polypide buds at the corresponding period, and 

 it is in fact a young colony while still free-swimming." 



In Pectinatella the so-called larval colony is freed from the 

 adult gelatin after an undetermined stay and may be obtained 

 in small numbers at certain times by sweeping around the adult 

 with a dip-net. Unfavorable conditions hasten the giving off 

 of these forms. Of two adults on the same stick, one partly 

 out of water due to a S. W. wind was giving off many more 

 larval colonies than the other. By bringing the adult into 

 the laboratory, the stimulus of the changed environment 

 results in the freeing of hundreds of these colonies. 



The earliest date at w^hich the free colonies have been 

 taken in the open water around the adults is July first in 



