Experiments on Polarity in Tuhularia. 581 



aboral end developed in two and a half days, and during the four 

 following days no others developed. 



In another set, after three days, one piece tied near the polyp 

 and one tied near the basal end had regenerated, and three days 

 later one of those tied near the middle developed a hydranth. 



In another set, after four days, one tied near the polyp and one 

 tied near the middle regenerated, and after three days more one 

 tied near the basal end developed. 



In two sets no aboral polyps developed. 



These results, as well as other similar ones, confirm Loeb's 

 statement that no definite relation exists between the time of 

 development of the aboral polyp and the length of the piece of 

 stem between the lio;ature and the basal end. Individual stems 

 behave very differently, but no connection between rate and 

 length of aboral pieces is apparent. So great is the difference in 

 time in different cases that difference in rate of development due 

 to another factor might be difficult to detect without more data. 

 In this connection the regeneration of the oral polyp, which takes 

 place more rapidly should be considered. Long pieces regenerate 

 a little sooner than pieces 7-12 mm. long, and in shorter pieces 

 (5 mm. or less) there is a longer delay. If a similar influence 

 was present at the aboral end in this experiment it might not be 

 detected. However, the length of the stem does not appear to 

 be, in either case, the principal factor that determines the rate 

 of aboral regeneration. 



Experiment 14. Another series of experiments, similar to the 

 above, was carried out in order to determine what influence the 

 changes involved in the development of an oral polyp have on tl.ie. 

 rate of development of an aboral polyp. 



{a) A check series of 10 pieces 15 mm. long was cut and tied 

 in the middle as soon as cut. The oral hydranths (10) came 

 out in from 19 to 68 hours, average 49.9 hours. The aboral 

 polyps (9) appeared in from 46 to 76.5 hours, average 69.8 hours. 



(b) 10 pieces 15-20 mm. long were tied in the middle 8 hours 

 after they were cut. The aboral hydranths (8) came out on an 

 average of 77.8 hours, just 8 hours later than those that were tied 

 at once. 



