206 H ARC ITT. [VOL. I. 



living specimens, though the colony had evidently suffered as 

 a whole. No particular attention was given them, and the later 

 growth of algae had seemed to entirely stifle the animal life of 

 the jar. A portion of the water was poured off and the jar 

 replenished from the laboratory tap, which is supplied from the 

 city water system. Once more the jar was set aside and un- 

 noticed for at least a fortnight, when, to my surprise, one day 

 the barnacles were seen to be living and active. This observa- 

 tion led to the introduction of specimens of Protozoa and Ostra- 

 coda from another aquarium to serve as possible food supply. 

 No further attention was given to the matter till incidentally 

 late in May, 1896, when from a cursory examination no life 

 was apparent except that of the Ostracoda, which had evidently 

 multiplied to considerable extent. The water was once more 

 poured off and once more renewed from the tap. Observations 

 made some time later revealed the presence of several colonies 

 of hydroids in apparently flourishing condition, and the bar- 

 nacles were also living and active. 



While the observations as a whole are interesting, those 

 aspects pertaining to the barnacles were specially so. While 

 these animals can endure long periods of removal from the 

 water, as removal above tide-water, etc., there is no record, so 

 far as I am aware, that they can endure changes so radical in 

 their nature as those above indicated. That the water was at 

 first saline to considerable extent was evident enough in the fact 

 of their presence in it. That they could endure a change to 

 practically fresh water is likewise evident. It is true that the 

 changes were not sudden ; and this would indicate the no less 

 interesting fact of the adaptability of the organism to changing 

 conditions of environment. 



Allman records that in his experiments he found that the 

 hydroids when changed from the slightly brackish water of the 

 Indian docks to that of fresh showed unmistakable signs of 

 decline, many of the hydranths falling from the stem and the 

 colonies as a whole showing decadence. On the additions of 

 slight portions of sea water they soon recovered and grew 

 freely. I have had similar results from the additions of small 

 quantities of salt to the water of the aquarium. 



