218 TEANSACTIONS OF THE [1892 



expelled from their mouths with unmistakable signs of dis- 

 comfort. In no case did I see a dabbler swallow a 

 hj^drauth, and they soon learned to avoid the colonies. 

 During the planula stage the darkness of the recesses may 

 be of some advantage in hiding them from organisms, which 

 might tend to devour them. The shade would also pro- 

 tect them from the direct rays of the hot summer sun, and, 

 as already mentioned, would tend to retard the evapora- 

 tion of moisture from the stems while above water, and 

 thus prevent destruction from desiccation (cf. 7. p. 254, 

 also 8, p. 26, note). 



ISTo break in the continuity of the Furnace Creek colo- 

 nies has, to my knowledge, been observed from the time 

 they were first seen by Professor Uhler. This observer 

 states that on one occasion he was unable to find specimens 

 of the hydroids at Cinder Cove, but he tells me that he 

 only looked over the surface of the dam and did not 

 examine its interior recesses. 



It is to be hoped that persons who may visit this locality 

 for specimens of Cordylophora will not more than neces- 

 sary molest the colonies which are attached to the dam, 

 for this is the only point near Baltimor-e yet known to 

 myself where the fully expanded hydranths can with cer- 

 tainty be obtained at any season of the year whatever. 



Owing to the fact that the Cordylophora of the Chesapeake was only 

 known to inhabit stations near the heads of estuaries where the fresh 

 water of the branches mingles freely with the tide water (v. 8, P- 32 ; cf. 

 also 5, p. 113), the impression has to some extent prevailed that the ani- 

 mal was practically a fresh-water species (cf. 7, p. 353), but we shall see 

 that it is able to flourish in Avater having a decidedly salt taste. I have 

 yet made no careful search for the hydroid in water known to be 

 entirely fresh. I once transferred some vigorous colonies from Cinder 

 Cove to an aquarium of aspirated hydrant water, and at the same 

 time others to an aquarium containing brackish water. The former, 

 unlike the latter, soon began to degenerate, and lived but a short 

 time. Dr.Andrews aptly suggests that one might be able to teach them 

 to live in fresh water by passing them slowly through intermediate 

 grades. 



