180 ANIMAL PARASITES AND MESSMATES. 



pillars, or the larvae of the coleoptera, orthoptera, or 

 diptera, and even to a mollusc, the Saccinea amphibia. 



Professor Meissner, and more especially Dr. Gre- 

 nadier, professor at Gottingen, have made known to us 

 the structure of the Gordius. The Gordius hifurcus pro- 

 duces embryos at the end of a month ; these embryos 

 perforate their shell by means of their beak, become free 

 in the damp earth, and introduce themselves through the 

 skin into the perigastric cavity of certain larvae. The 

 sexual worm again becomes free. If we may believe 

 Mons. Villot, who has made recent observations on the 

 Mermis and the Gordius, the latter alone pass through 

 complete metamorphoses ; they assume three different 

 forms, and change their habitation three times. Their 

 first abode must be in the water, or in the larva of 

 a dipterous insect, as a free embryo ; the second in the 

 larval state, in the intestines of a fish ; and the third, 

 like the first, in a sexual state. 



To judge by some specimens of gordius brought from 

 India, these curious parasites exist not in Europe only ; 

 they have been found in different parts of the world, and 

 they lead everywhere the same kind of life. 



They have been found in Calcutta in the Hapale; 

 in the Philippine Islands in a Mantis, and the museum 

 of Hamburg possesses some from Venezuela, which came 

 from the body of a Blatta, 



These worms, when they approach the adult and 

 sexual age, lose their various external organs, and are 

 so completely modified with respect to their organization, 

 that at last they are merely a case for eggs. They are 

 so entirely egg-cases, in which the digestive tube and 

 the other organs disappear in proportion as the sexual 



