New Infusoria from American Fresh Waters. 437 



consisting of large nucleated cells." A similar affection is 

 found in this species at St. Andrews and in the Thames, and 

 the same tumours occur on the plaice. 



In a male example of the latter, for instance, the coloured 

 surface is crowded with small rounded tumours which re- 

 semble shot. They are also attached to the various fins 

 (PI. XVI. fig. 6) as well as invading the white surface. They 

 are firmly fixed to the skin, give pain when interfered with, 

 and are vascular. The isolated tumours range from 1*7 millim. 

 to 1 millim. or less ; the larger masses (PI. XVI. fig. 6, a), 

 when bisected, show a series of smaller areas, the whole being 

 composed of multiple tumours, mostly of the same size 

 (PI. XVI. fig. 7) . In the fresh state section is followed by 

 the exudation of a minute granular whitish creamy substance, 

 and the occurrence of fine fibrillaa under examination indicates 

 that the fluid is probably coagulable. Each chamber is cystic, 

 presenting a firm hyaline wall of considerable thickness, 

 bounding the granular contents. The stroma exterior to the 

 former is chiefly fibro-granular. Smaller cysts in course of 

 development are observed amongst the stroma, the thick 

 translucent hyaline w r all being conspicuous. These tumours 

 therefore would appear to differ from the kind with nucleated 

 cells described by Lowe. 



EXPLANATION OF PLATE XVI* 



Fig. 1. Transverse section of the ovary of Zoarces vivipanis, shortly after 

 the escape of the embryos, a, epithelial coat ; b, muscular 

 layer; c, section of the blood-vessels at the margins of the 

 villi, x about 40 diam. 



Fig. 2. A fragment of the membrane of a villus, showing the large ana- 

 stomosing vessels. Magnified. 



Fig. 3. Ova of Cychpterus lumpus. About the natural size. 



Fig. 4. Ova of Cottus scorpius. About the natural size. 



Fig. 5. Ova of Liparis Montagui. About the natural size. 



Fig. 6. Portion of the anal fin of a small Pleuronectes platessa, with a 

 multiple tumour and a few detached masses. About natural 

 size. 



Fig. 7. Transverse section of the foregoing multiple tumour. Enlarged. 



XL. — Some new Infusoria from American Fresh Waters. 

 By Dr. Alfked C. Stokes. 



[Plate XV.] 

 The following hitherto undescribed Infusoria were originally 

 met with in shallow ponds in central New Jersey, or were 

 * I have to thank Mr. Ed. Prince, Assistant-Zoologist at the Marine 

 Laboratory, for the careful drawings in this Plate. 



