220 TKANSAOTIONS OF THE [1892 



During the early days of May the colonies were found in 

 excellent condition, but when I examined them on the 

 22d of that month I noticed that they were not as vigorous 

 as before. The water was beginning to show the impuri- 

 ties derived from the city, and the stems of the colonies 

 were becoming loaded with Vorticellae. In July I found 

 that over all of the piles, where I had earlier observed 

 tiourishing colonies of Cordylophora, dense and beautiful 

 growths of Bryozoa, which were so thick that I could peel 

 large mats of them from their base of support. Only an 

 occasional stem of Cordylophora could be found which had 

 not been crowded out by its molluscoid rival. Late in 

 September, and again on October 25th, I was unable to 

 lind any trace either of the hydroid or the bryozoan.* 

 October 30th I visited the Cinder Cove colonies in order to 

 determine whether they too had. disappeared, but found 

 them unchanged. 



Last June my nephew found some good specimens of our 

 hydroid attached to the sides and lower surface of a small 

 floating dock at Flood's Landing, Spring Gardens. These 

 colonies, like those at Fort Covington at a similar date one 

 year previous, were being crowded out by dense growths 

 of Bryozoa. 



On- the 26th of March, 1891, I visited the old so-called 

 Sliell Wharf, at River View, in search of colonies. This 

 dock lies immediately below the new Northern Central 

 elevator. Near the outer end of the dock, on its eastern 

 side, I found a pine board nailed fast to the same and 

 projecting vertically several feet into the water. The 

 board was well worn, and had evidently been in this posi- 

 tion for several years, I pried it loose, and found upon its 



* Last May I found the Fort Covingtou colonies again in good condition. Tliat 

 this temporary disappearance was due to the presence of certain elements in the 

 water near the city, which were either directlj' injurious to them, or indirectly so 

 through the undue nourishment of their competitors, is suggested by the fact 

 (later to be mentioned) that several miles below the city the colonies persist 

 throughout the summer and autumu months. 



