LOCOMOTION IN YOUNG COLONIES OF PEC- 

 TINATELLA MAGNIFICA. 



ALICE W. WILCOX. 



Pectinatella magnified is the largest of the fresh -water bryozoa 

 (Phylactolaemata). It is a distinctively American form and is 

 generally known by the conspicuously large masses of it, which 

 are formed in the late summer and fall. These masses com- 

 monly are as large as a man's head and often attain the size of 

 sixteen by eight or nine inches. They are found floating or at- 

 tached to submerged solid material in some of our purest fresh- 

 water ponds and reservoirs. Each of these masses consists of a 

 thin coating of Pectinatella colonies attached to a thick sub- 

 stratum of transparent, colorless jelly. The colonies are diamond- 

 shaped in general form, with many slender, radiating lobes, each 

 bordered by a double row of actively-contracting polypides. 



These jelly masses are one of the most unique phases of the 

 life-history of the species. In order to understand their mode of 

 formation, I undertook a preliminary study of the growth and 

 behavior of the young Pectinatella colonies. This resulted in the 

 discovery that during their early stages these colonies have the 

 power of independent motion. This paper gives the evidence of 

 this fact of locomotion in young Pectinatella colonies. 



It was long believed that the power of locomotion in the 

 bryozoa was confined to the genus Cristatella, of which it is a 

 striking characteristic. But a Danish zoologist, Wesenburg- 

 Lund ('96), discovered that another genus of the Phylactolsemata, 

 Loplwpus, has this power of independent locomotion. He observed 

 that the young LopJiopus colonies sometimes migrate six centi- 

 meters in the course of twelve hours. 



In 1901 I studied young colonies of Pectinatella magnified 

 undermost favorable conditions at Cold Spring Harbor, L. I. 

 There Pectinatella occurs, in abundance in three connecting fresh- 

 water ponds. Flood-gates separate the adjacent ponds and to 

 these the statoblasts of Pectinatella often attach themselves and 



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