334 H. S. DAVIS 



II. MATERIAL AND METHODS 



The Myxosporidian, which I have named Sphaerospora di- 

 morpha, is abundant in the urinary bladder of Cynoscion re- 

 galis, extending into the Wolffian ducts in large numbers, but 

 I have never found it in the kidney tubules proper. The para- 

 site occurs as two very different forms, one disporous, the other 

 polysporous, although both forms are usually present together in 

 the same host. A large number of fish were examined and in no 

 case was the bladder found to be entirely free from infection 

 although there was great variation in the abundance of the 

 parasites. The results incorporated in this paper are based on 

 the study of a large amount of material, both fresh and preserved. 



For studying the living trophozoites a small amount of ma- 

 terial was taken from the bladder in a pipette and transferred 

 to a slide where it was studied at once.^ To prevent evapora- 

 tion the cover was at first ringed with vaseline, but later paraffine 

 of a low melting point was found to be much superior for this 

 purpose and was thereafter used exclusively. Under these con- 

 ditions it was possible to keep the trophozoites for several hours 

 without any appreciably bad results. However, after six or 

 eight hours the trophozoites usually showed distinct signs of 

 degeneration, probably due to the rapid increase of bacteria in 

 the preparation. Attempts were made to grow the trophozoites 

 on agar culture media but without success, although they lived 

 somewhat longer under these conditions than on the slide. 



In studying preserved material both dried smears and sec- 

 tions were used. In preparing the smears a small amount of 

 material was removed from the bladder with a pipette and 

 smeared thinly over a coverglass which was then exposed to 

 osmic vapor for 30 to 60 seconds, after which the preparation 



- Since the parasites are commonly attached to the lining of the urinary bladder 

 it was found in practice that to insure getting a large number of trophozoites it 

 was first necessary to allow most of the urine to escape. This was done by slit- 

 ting the wall of the bladder with the scissors, allowing the urine to flow out, and 

 then by applying the mouth of the pipette to the inner wall and forcibly sucking 

 up the remainder of the contents the parasites could invariably be obtained 

 in large numbers. 



