HELMINTH FAUNA OF THE DRY TORTUGAS. 

 II. TREMATODES. 



By Edwin Linton. 



INTRODUCTION. 



The collection here described was made at the Marine Biological 

 Laboratory of the Carnegie Institution, Tortugas, Florida, in the sum- 

 mers of 1906, 1907, and 1908. In each season my stay at the Labora- 

 tory was about three weeks. Without exception the fishes examined 

 were from the shallow waters of the reef. Tables showing the distri- 

 bution of parasites together with food notes have already been pub- 

 lished in the Year Book of the Carnegie Institution of Washington for 

 the years above named. 



While the exact method of collecting material varied with the size 

 and number of the hosts, in general I found it best to open the alimen- 

 tary canal, wash out the contents with sea-water, wash and decant 

 several times if necessary, and then collect the small distomes with a 

 pipette. The distomes were killed in various ways, hot corrosive sub- 

 limate, picro-sulphuric acid, etc. A very satisfactory way for whole 

 mounts is a method used by Fuhrmann, viz., kill in 70 per cent alcohol 

 and stain in very dilute hasmatein. Preliminary to this it is a good 

 plan to flatten the distome under a cover-glass and heat it a little before 

 placing in the killing fluid. My best sections are from material fixed 

 in picro-sulphuric acid, although material killed in hot corrosive sub- 

 limate and stained with carmine is usually very satisfactory. In spite 

 of precautions much material which one collects proves unsatisfactory 

 or difficult. In many of the smaller distomes the vitellaria conceal the 

 general anatomy. In other cases the uterus is so full of eggs that other 

 parts are obscured or displaced. Again, the spinose cuticle is often 

 evanescent, and one is frequently much puzzled over a specimen that 

 has a close resemblance to forms with spines, but which is itself entirely 

 destitute of spines or of any certain indications that it ever had spines. 



All measurements are given in millimeters. 



Where no other habitat is mentioned the intestine is to be under- 

 stood as the habitat. 



I am disposed to think that modern helminthologists have unduly 

 narrowed the idea of genus among the distomes. At the same time I 

 recognize the futility of attempting any change at present in the con- 

 ception of what should constitute a generic character in this difficult 

 group. Therefore, since I find it quite impossible to secure an abiding- 

 place for a majority of the Tortugas distomes in any existing genera, 

 I have thought it best to make new genera rather than to extend the 

 limits of genera that have been established. It has been my aim to 



15 



