ON ENTOZOA. 557 
cumstance, at the same time that the body is continually 
shooting out, finishes by giving to the latter a very variable 
length, but which sometimes exceeds two feet. We may 
then observe some of these articulations, and more fre- 
quently the posterior ones, fill by degrees with eggs, of 
somewhat a different bulk, but of the same oval form, and 
which after they issue forth, in their turn produce young 
bothryocephali. 
There are two interesting questions respecting the deve- 
lopment of the intestinal worms; first, can such and such 
species only, be developed in the body of such and such ani- 
mals, and may not this development be sometimes continued 
in another animal ? 
The successful experiment of Pallas, in introducing the 
eggs of the tenia elliptica, into the abdominal cavity of a dog, 
is a reply to the first question. 
As for the second, it appears certain that the ligula, when 
it is found in fishes, never presents itself in the adult state, or 
with developed ovaries, which is quite the reverse of what is 
observed when it is taken in an aquatic bird. M. Rudolphi, 
therefore, supposes, that born in the fish, it only acquires its 
full development in passing into the birds, and that this is 
owing to the heat of their body. He brings forward, more- 
over, in support of this opinion, the case of a bothryocephalus, 
which in the imperfeci state (B. solidus,) is found in a spe- 
cies of gasterosteus, and in the adult state (B. nodosus,) in 
aquatic birds only. He further explains by this, the curious 
fact, that in the northern countries of Germany, and in Den- 
mark, where this little fish is common, the aquatic birds are 
infested with the B. nodosus; while in Southern Germany, 
where this gasterosteus does not exist, the aquatic birds have 
not this bothryocephalus. 
We shall particularize only one species of this disgusting 
