462 STANLEY C. BALL 



II. BIOLOGY, IMATERIAL AND METHODS 



Biology and material 



Paravortex gemellipara was stated by Linton to be a com- 

 mensal living on the gills of Modiolus demissus, but Patterson 

 concluded that the worm lives primarily in the kidney, although 

 he thinks it likely that many individuals escape and may then 

 be found in the mantle cavity and on the gills. Patterson opened 

 two dozen mussels, using care not to injure the tissues. When 

 washed in water no parasites were found, but after tearing 

 the kidneys of these same mussels apart, he secured thirty- 

 eight specimens. Hallez ('09) found P. cardii in the stomach 

 and intestine of Cardium edule. So, thinking that in attempt- 

 ing to dissect the kidney, Patterson might have cut the alimen- 

 tary canal, I made several attempts between May and Septem- 

 ber to discover the worm in the stomach, intestine, kidney and 

 liver. 



After the adductor muscles alone had been carefully cut and 

 the valves forced apart eight to sixteen mussels were vigorously 

 washed in sea water. If more be opened at once the sediment 

 renders the Turbellaria difficult to detect. The worms were 

 allowed to settle to the bottom, and, the better to see the bottom 

 of the dish, most of the water was slowly decanted. The vessel 

 was then placed upon a dark surface in good light. In looking 

 for the very young a hand lens was found useful. Next the 

 stomachs of the same mussels were carefully slit open with 

 dissecting scissors and the interior washed in another dish by 

 means of jets from a pipette. Water was also forced through 

 the intestine in the same manner. Finally, in a third vessel, 

 the same mussels were again washed after tearing apart all 

 the tissues, thus insuring the breaking open of the kidney, 

 an organ extremely difficult to distinguish and dissect without 

 disturbing other tissues. 



It was found that two hundred thirty-seven mussels collected 

 at various times during the year yielded with the first washing 

 one hundred eleven specimens of Paravortex, with the second 

 two and with the third six. In one instance thirty-seven worms 



