410 J. STAFFORD, 



a favourable measurement. It was perhaps of the same size as the 

 largest described byLooss while the normal ones are smaller, of the 

 size given by Sonsino and Creutzburg, about 5 or 6 mm. 



An Illustration, literature, anatomy etc. are given in the book 

 by Looss. 



4. JDistotnuni tetracystis Gastaldi. 



This form I observed two years ago and in great numbers — 

 apparently hundreds — in the thoracic cavity of small grass frogs. 

 Being occupied with other work at the time, I did not follow up the 

 question. lipon slitting open the ventral wall including the Shoulder 

 girdle, these Trematodes could be drawn off in a pipette from the 

 region in front of the heart. They were entirely free in the lymph 

 which flowed into the thoracic cavity and I thought that it was pos- 

 sible that they came from some lymph spage between the muscles. As 

 they were all free I did not suppose that I had the same species as 

 that of Gastaldi. 



A week or two ago I directed my attention again to this subject, 

 using the bull-frog {B. catesUana). I find the worm encapsuled, in 

 great numbers, in the region of the throat. By removing the skin, 

 slitting through the mylohyoid muscle and liftiiig up the cartilaginous 

 anterior end of the sternum, the capsules are exposed, lying imbedded 

 in a gelatinous mass that extends over a considerable space, reaching 

 back to the level of the heart and also spreading outwards and back- 

 wards to the attachment of the anterior limbs. It was by cutting 

 through this mass that the worms were freed in such numbers into 

 the thoracacic cavity, upon my first noticiug them. Only a few days 

 ago, however, I found a huge gelatinous mass containing abundance of 

 Worms lying on the duodenum in the position of the pancreas which 

 appeared to have been destroyed. 



The capsules measure about 0.8 mm by 0.7 mm and smaller, and the 

 thickness of their walls is 0.085 mm. The worms are able to free 

 themselves rapidly from their delicate, connective-tissue capsules as 

 shown by the great numbers that speedily become free when disturbed. 

 Gastaldi's .^) description although brief is remarkably correct, 



They are immature worms, about 700 /< long when alive, but 

 possessed of great freedom in lengthening and shortening their bodies. 



1) BiAGio Gastaldi, Cenni sopra alcuni nuovi elminti della Rana 

 esculenta, Torino 1854. 



