1892] MARYLAND ACADEMY OF SCIENCES. 217 



the cove submerged, at high tide, to a depth of one foot 

 or more, and after prolonged westerly winds I liave seen 

 the tide-water retreat, at low tide, several yards from the 

 foot of the dam, leaving many of the growths for several 

 hours exposed to the atmosphere. Indeed, at the average 

 low tide, when the wind is quiet (PI. II), many of the 

 growths are thus exposed. Were it not for the fact that 

 while thus exposed they are kept moist by the (more fresh) 

 water of the tide-pond, and of the branch which flows 

 into it, which continues to pass through the above de- 

 scribed lateral channel (PI. II), and by the water retained 

 among the lower recesses of the dam, they would soon 

 become exterminated through the eftects of desiccation. 



"Within the recesses of the dam the colonies are usually 

 best developed. Even during the winter months, when the 

 cove contained ice, I found that the stems in the more 

 remote recesses still bore hydranths. Several advantages 

 would seem to be gained by living in these recesses, among 

 which should be mentioned the protection which they afford 

 from the ice, siiow, and extreme cold of the winter months ; 

 and during the summer from the dry atmospheric currents 

 which would tend to carry away their moisture while 

 above water. From the deep shade or darkness of these 

 recesses at least three advantages would be arained: 

 first, protection from enemies which might tend to prey 

 upon them. I doubt, however, whether the adult Cordy- 

 lophora is in serious need of defence from enemies beyond 

 that which is afforded by the nettle cells of its tentacles. 

 I once placed some Mud Dabblers, which were strangers 

 to Cordylophora, in an aquarium with the colonies, and 

 watched their attempts to crop the hydranths. As soon 

 as their mouths came in contact with the tentacles, the fish 

 darted away as though in pain. I cut off a hydranth and 

 dropped it into the water. It was immediately seized by 

 first one and then another of the fish, only to be instantly 



