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FRANK M. SURFACE. 



short distance and then draw back, often repeating this several 

 times. Thus each individual pushes some distance beyond the 

 previous limit, but at last it usually turns around and moves back 

 towards its fellows. This like certain observations previously 

 mentioned seems to indicate that the adhesive thread which they 

 always secrete as they move about, furnishes a guiding stimulus 

 for the young rotifers. Sometimes an individual leaves the stem 

 and swims a short distance from it, always attached by the thread. 

 By such movements the whole ball finally breaks up and the 

 individuals are seen moving back and forth along the stem, some- 



FIG. 2. Sketch showin the young ball (/>) breaking up into free swimming indi- 

 viduals and the permanent colony forming at c. 



times venturing quite a distance from the majority of the. colony. 

 But soon a few individuals settle down at some point and remain 

 fastened by their posterior ends, with the body projecting at right 

 angles from the stem (Fig. 2,<:). Soon other individuals attach 

 themselves in a similar manner with their posterior ends close to 

 those already attached. This is the beginning of the formation 

 of the permanent colony. In a comparatively short time all of 

 the young animals have attached themselves in a closely aggre- 

 gated group surrounding or nearly surrounding the stem. This 

 permanent colony may be formed close to where the ball broke 



