7 i4 THE RAY- WORM. 



enemy had been destroyed. It is rather flat, like some kinds of silken thread, and is 

 of a very pale brown color. 



Passing by a few genera, such as Ascaris, Tricocephalus, and Strongylus, all of 

 which are found in the human subject, we come to the large and important genus Taenia, 

 which may be accepted as the type of all the Entozoa. The well-known Tape-worm 

 (Tcenia solium] belongs to this genus. It derives its name of solium as also its French 

 title of Ver Solitaire, from the supposed fact that only one individual can infest the 

 same person. It is, however, known that a few cases have occurred where the same 

 individual has been afflicted with, at least, two specimens of Tape-worms. Those 

 which belong to this genus may be known by the long flat body, and the head with 

 four suctorial spots, and almost invariably a circle of very small, but very sharp, 

 hooks. The whole structure of the Taenia is interesting to those who study comparative 

 anatomy, but too purely scientific to be described in these pages. 



The upper figure in the preceding illustration represents a species of Tape- worm that 

 is found in the common cat ; and the lower figure affords an example of a Tape-worm that 

 is found in several birds, such as the nightingale, blackcap, and the bird from which it has 

 derived its popular name. This figure is intended especially for the purpose of showing 

 the peculiar head, with its four suctorial disks. Another example of this genus is seen in 

 the next illustration, exhibiting the curious head, and the extraordinary difference of 

 size between the segments of the body. This species is found in the black-backed gull. 



THERE is another notable genus of Entozoa, commonly going by the name of Hy- 

 datids, on account of the large amount of liquid which is found within their cells. 

 Within each large cyst, or cell, myriads of smaller cysts may be found, some in an early 

 stage of progress, and others being further advanced, and containing other cysts within 

 themselves. 



I have seen some enormous Hydatids taken from the interior of a female monkey. 

 They were so large, and so full, that the owner of the animal thought that it had died 

 from over-eating itself. On opening the creature, however, the stomach was found to 

 contain very little food, and almost the whole cavity of the chest and abdomen was 

 filled with huge cysts, which had encroached upon all the vital organs, pushed the heart 

 on one side, enveloped the whole of one lung ; and, in fact, had caused so strange a 

 disturbance of the viscera, that the fact of the creature having supported life under 

 such circumstances seemed almost incredible. The large cysts contained a vast number 

 of smaller cells, and these again were filled with cysts of still less dimensions. A large 

 quantity of fluid also existed, and floating in the liquid were found myriads of echinococci, 

 very small, but with the characters exhibited perfectly well under the microscope. 



WE now come to our last example of the Entozoa. 



The RAY-WORM is, as its name imports, an inhabitant of fishes belonging to the ray 

 tribe. The genus to which this creature belongs is a rather remarkable one, the head 

 affording some curious characteristics. As may be seen, it is very large in comparison 

 with the body, and has four deep clefts set opposite to each other. Some of the species 

 have only two of these clefts, which, in the Greek language, are called "bothria," but 

 in all the genus either two or four of these clefts are to be found. The generic title 

 literally signifies " furrow-headed." 



One species of this genus (Bothriocephalus latus) is the well-known BROAD TAPE- 

 WORM, which is so injurious to man whenever it takes up its abode within a human being. 

 This creature will sometimes attain a length of twenty feet ; and it may always be 

 recognized by the peculiarly deep and opposite furrows on the head. Like all its kind, 

 this Tape-worm increases with great rapidity, multiplying its joints by division, and 

 in that manner extending itself to the great length which has already been mentioned. 



The whole history of these strange creatures is very obscure, on account of the 

 impossibility of watching them in the spots wherein they take their residence. They are 

 all, as is generally the case with beings low in the scale of nature, exceedingly tenacious 

 of life, and will survive treatment which would kill many beings apparently stronger and 



