126 REPORTS ON INVESTIGATIONS AND PROJECTS. 



Report upon Tortugas Trematodes, by Henry S. Pratt, of Haverford 



College. 



I revisited the Tortugas Laboratory this year for the purpose of making 

 further collections of trematodes from the fishes of the region, in order that 

 the collections of last year might be supplemented and the morphological 

 studies already begun completed. I wished also to study again the live worms 

 of several species of unusual interest and importance of which I have pre- 

 served material, trematodes being so extremely contractile that it is often 

 necessary to study them alive in order to determine accurately the arrange- 

 ment of the organs. 



One of the most interesting worms obtained last year was a monogenetic 

 trematode belonging to the genus Monocotyle, which lives on the gills of 

 the whip-ray (Myliobatis freminvillei). This trematode differs from other 

 similar worms in several important structural details, e. g., the union of the 

 intestinal trunks at their posterior ends and the presence of a rectum-like 

 ccecum which extends straight back from the point of juncture of the paired 

 intestines to the extreme hinder end of the body. In two of the individuals 

 examined this ccecum opens to the outside through a median dorsal pore 

 which has the exact appearance and position of an anus, although in all the 

 other individuals no such opening was seen. These unusual features made 

 it important to reexamine the animal in order to determine, if possible, to 

 what extent they have phylogenetic significance. A whip-ray was fortu- 

 nately obtained and a large number of the worms in question were collected. 



Other worms which it was important to reexamine were several species 

 belonging to the subfamily Allocreadinae, which occur in the gray snapper, 

 the grunts, the angel-fish, and the groupers. The worms of this subfamily 

 have excited a good deal of interest recently among helminthologists, and 

 attempts, not altogether successful, have been made to monographize them. 

 The existence of six or eight new species in the Gulf of Mexico makes the 

 Tortugas Laboratory a particularly favorable locality in which to study the 

 subfamily. 



Besides these worms, the study of which was the principal object of the 

 visit, I also collected about twenty species of trematodes belonging to other 

 groups. 



Report on Annelids, by A. L. Treadzvell, Vassar College. 



The work at the Tortugas was a continuation of that begun in 1909, on 

 various problems of annelid morphology, including the phenomena of the 

 swarming of the Atlantic palolo. In 1910, this swarming occurred on the 

 mornings of June 29 and 30, the last quarter of the June moon falling on 

 the 29th. There seemed reason to expect further swarms near the time of 

 the first quarter of the July moon, but none occurred at this time. 



Pomatostegus stellatus larvas of the third day settle to the bottom and 

 begin to secrete their calcareous shells. In 1909 a number of these were 

 collected on tiles and placed in the moat at Fort Jefferson, to determine the 

 rate of annual growth. These did not live, and the experiment was re- 

 peated in 1910. To determine if the larvas orient themselves with reference 

 to light rays, they were allowed to settle on glass plates in a dish illuminated 

 from only one side. In their first position of fixation and in the direction 

 of subsequent growth of the shell, for at least the first three weeks there was 

 absolutely no indication of light orientation. 



