TKANSMIGRATIONS AND METAMORPHOSES. 237 



We see that all means are good that are for the 

 preservation of the species, but who would have suspected 

 that in a single animal there would be found two males 

 by the side of two females, neither of which resembles 

 the other, and besides these, two kind of eggs and sper- 

 matozoids ! How great would be our astonishment 

 were we to see two sorts of cocks, two kinds of hens, 

 and two sorts of eggs produced by the same mother, 

 and hatched at the same time ! 



Professor Ercolani bred in damp earth certain para- 

 sitical nematodes, kept them alive, saw them reproduce, 

 and was even able to obtain several generations of them. 

 These nematodes were the Strongylus filaria fi-om the 

 lungs of the goat, the Strongylus armatus from the in- 

 testines of the horse, the Ascaris inflexa, and the 

 Ascaris vesicularis from the fowl, and the Oxyuris in- 

 curvata from the horse. The first three, whether they 

 are born in damp earth, or in the midst of organs in 

 which they habitually lodge, have the same external 

 characters; nothing is remarked in them except a greater 

 activity in their rejDroduction. 



The Strongylus armatus, when born at Hberty, appears 

 no longer to have hooks at the mouth like those worms 

 which hve in the intestines. Mons. Ercolani has also 

 remarked that these worms, when they become free, are 

 ovo-viviparous, though they were before oviparous. 



There are many of these nematodes which are true 

 parasites of man, and although certain of these are as 

 much dreaded as the plague or the cholera, we are far 

 from knowing all their history, and especially the manner 

 in which they are introduced. 



A young naturalist, Dr. 0. Biitschli, has lately made 



