FISH PARASITES COLLECTED AT WOODS HOLE. 301 



On the Occurrence of Cysts in the Stomach Wall of Pomatomus saltatrix. 



[Plato 42, litf. 101, U. S. N. M. No. 0529.] 



A piece of the stomach wall, about 8 mm. square, comprising the, mucosa and submuco.-,a taken 

 from tbc stomach of a blue-fish July 23, was stained in borax carmine, and sectioned. 



One of these sections, measuring 8 mm. in length, had passed through six distinct cysts, each 

 containing, so far as it was possible to determine, a larval Tetrarhynchus. Some of the cysts contained 

 embryos which were too young for certain identification. The combined length of these cysts was 

 3.5 mm. The superficial area included in the sections of these cysts represented two-lifths of the 

 area of the submucosa of the entire section. If this ratio of cysts and snbmucosa were maintained 

 throughout the stomach of the lish it would follow that something like 12 per cent of the tissue of the 

 stomach consists of foreign tissue if not actively inimical to life at least passively so. The amount of 

 energy consumed in building up the protective cysts about these embryos, and of digested and absorbed 

 food which is diverted to the use of these vagrants, must bo considerable. The above is possibly some- 

 what above the average, although it may be below it, for it is a common thing to find the submucosa of 

 the stomachs of blue-fish, squ.ctea.guc, flounders, etc., so full of cysts that the space occupied by the cysts, 

 as seen on superficial view, appears to be quite as much as the space remaining between the cysts. 



The outside wall of each cyst consists of connective tissue libers in concentric circles, compact 

 but merging in places into the connective tissue elements, with numerous nuclei. Within this is 

 the cyst proper, the outer layer of which stains deeply in carmine and is made up of a few concentric, 

 plate-like, structureless layers, which are somewhat brittle. Within this is the blastocyst. The outer 

 layer of blastocyst and the closely underlying muscular elements stain moderately, but the inclosed 

 parenchyma, which makes up the interior, stains very little. The embryo, on the other hand, stains 

 quickly and strongly in carmine. The parenchyma in these sections is an opened mesh work of unstained 

 tissue, with sparse nuclei scattered through it. Near the boundary the nuclei become abundant. 



The above-mentioned membranes were measured in one cyst with the following result, dimensions 

 in millimeters: Thickness of outer nucleated connective layer 0.02, of inner non-nucleated layer 

 0.007, of outci layer of blastocyst 0.007. 



Cysts from Kidneys of Scup. 



[U.S. N.M. No. 6530.] 



Small globular cysts were found in the kidneys of a scup (Stenolomtm diryaopx') August 4. These 

 cysts were about 1.5 mm. in diameter. Two of them were opened, but nothing could, be made out of 

 the contents. There were also small blotches of black pigment on the surface of the kidneys. 



A few of these cysts were sectioned, with the following result: The cysts appear to be small 

 tumors, 1 mm. or less in diameter. They are composed entirely of connective tissue and are exceed- 

 ingly compact. Toward the periphery of the tumor there is a concentric arrangement of the fibers 

 which is quite distinct, portions showing a tendency to separate, or rather to become slightly loosened 

 from the general mass. Though this concentric arrangement was traceable from the greater part of the 

 periphery well toward the center, it was lost near the center, and at one side was indistinct. Nuclei 

 were abundant throughout the mass. Only the tumors, with what tissues remained adherent to them on 

 removal from kidneys, were preserved ; but the sections disclose an abnormal condition of the adjacent 

 tissues in that they are infiltrated with blood so as to resemble a blood clot with a few uriuiferous 

 tubules penetrating it. In this infiltrated tissue lie also numerous small black pigment masses. 



Such conditions call for further investigation to bring out the actual structure and the extent to 

 which the tissues are affected. No nucleus could be distinguished in any of the tumors sectioned. 



On Cysts in Stomach-wall of the Black Sea-bass ( Centropristes striatus). 



[Plate 42, tigs. 103, 104, U. S. N. M. No. 6531.] 



A number of sections were made and mounted serially of a part of the stomach-wall of a black 

 sea-bass, collected July 28. A study of these sections reveals the fact that some of these cysts are 

 formed around blastocysts which contain larva;. In a few cases they were developed far enough to 

 show by the character of the hooks that they were near if not identical with forms already described 

 from this host. (Notes on Larval Cestode Parasites of Fishes, pp. 793-794, pi. n, fig. 12.) Others are 

 too young to admit of identification further than that they represent the early stage of some cestode 

 worm, but presumably most if not all of them belong to the genus Rhynchobothrium, and possibly 

 to a single species. 



