1890.] NEW-YORK MICROSCOPICAL SOCIETY. 81 



marine aquaria — oxydizing the water with the two algae, the green 

 sea lettuce, Ulvalatissima and the red coral like Gracilaria multi- 

 partita. Soon the infusoria appeared, and soon after came fine 

 crops of diatoms. My plan was to put the four fishes into one 

 of these small aquaria, allowing them possession until I supposed 

 their food was reduced ; then I transferred them to another, and 

 in time to the third, after which they went back to No. i. By 

 this routine or interchange their supply of food was sustained, 

 the water being kept well stocked with microscopic life. 



In about four months, I made what seemed to me an interest- 

 ing observation. It was the fact that these little creatures had 

 the faculty of mimicry. In respect of color, their normal hue 

 was that of a slaty or yellowish grey. From this they could take 

 on two extremes, becoming either almost black, or even an ashy 

 white. This latter fact led to a deception, for noticing in one 

 of the Hippocampi certain white spots of rather long continu- 

 ance, I misinterpreted the fact — as partial, or deceptive mim- 

 icry. At length I beheld to my dismay, a white blister, with 

 some indications of uneasiness by the fish. It recalled the ex- 

 perience of two years before. The vesicle was at once pricked 

 with a needle — but the nialady spread over the body, when it 

 soon died. 



As I was then in the midst of my study of Saprolcgnia, I lost 

 no time in getting an almost invisible scraping of the skin 

 under the microscope, when lo ! my scorbutic hypothesis " went 

 up " leaving me with another fungus of a singular character on 

 my hands. In size the new plant compared with the Saprolcgnia 

 was as the little fern to the sturdy pine under whose shade it 

 has grown. 



I found some difficulty in the study of this object due to its 

 extreme minuteness, and the crystalizing of the salt in the sea- 

 water which would proceed in each mount, thus burying or 

 breaking up the plant. It became necessary to wash away the 

 salt, to the cruel cost of a sad waste of material, and a pitiful 

 destruction of the natural grouping. With these disadvantages, 

 after a number of trials some success was achieved in eliminat- 

 ing the salt, and some fair mounts were made in carbolated 

 glycerine. 



In a few days another fish died, and in about three weeks all 



