G4 



STARFISH GALLERY. 



solium, the common Tapeworm of man in Northern Europe. 

 This worm is matured in the intestines of man ; its final joints 

 consist merely of fertilized ova which have already passed through 

 the earlier stages of development ; when 

 the joints are detached and discharged, 

 their contents escape in the form of 

 embryos contained in a thick chitinous 

 shell. If these are now swallowed by 

 a pig, the shell is digested by the gastric 

 juices of the new host, and a rounded 

 embryo, which is provided with three 

 pairs of hooks, is set free ; by means of 

 these hooks the guest makes its way 

 through the wall of the stomach or in- 

 testine, and finally settles down in the 

 muscles of its host. The embryo now 

 loses its hooks, and gradually acquires 

 a bladder-like form, the central cavity of 

 which is filled with fluid. This bladder- 

 worm (Cysticercus) has its outer wall 

 pushed inwards at the anterior end, and 

 on this hooks and suckers become deve- 

 loped. We have now a narrow head and 

 neck with an attached bladder, the head 

 being at this time hollow. If during 

 the long time that these bladder-worms 

 remain alive, the pig is killed for food, 

 its flesh is found to be " measly " ; if it 

 is afterwards insufficiently cooked and 

 eaten, the worms are conveyed into the 

 human stomach. Here the bladder-like 

 termination becomes absorbed, and, the 

 neck beginning to grow, we have the commencement of the form from 

 which we started, and the completion of that "vicious circle" which 

 is so curious a characteristic of many forms of parasitic life. 



In other Tapeworms the cyst may be more complicated than that 

 in the pig, as, for example, the form found in the sheep's brain or 

 the liver of the horse. 



Taenia solium : showing the 

 head (/<) with its suckers 

 («') and crown of hooks 

 (s), the unjointed neck 

 («), and a few of the 

 succeeding joints (J). 



