Miscellaneous. 



the trachea ? If the thoracoabdominal cavity be filled by a blue 

 nutritive fluid, why should not the walls of the tracheae, which, like 

 all the tissues of the organism, require nutrition and reparation, be 

 also penetrated by these blue particles ? Is it necessary, in order to 

 explain this coloration, to recur to an intermembranular cavity, the 

 existence of which I think I have sufficiently disproved by facts and 

 arguments ? 



Perhaps, in regard to the absence of coloration in the ramifications 

 of the tracheae, M. Blanchard will intrench himself behind these 

 words in his communication — " The tracheae present the deepest tint 

 at their base, becoming gradually paler to the extremity." This ar- 

 gument may appear valid if we only regard one of these canals sepa- 

 rately ; but, as every one knows, the isolated filaments of a blue cocoon 

 do not appear blue, although the whole of the filaments produce a 

 blue cocoon, — and the same effect must take place in the living tis- 

 sues of an insect, when the blood-vessels, however capillary they may 

 be, become pressed together in close ramifications for the performance 

 of their nutritive functions. — Gomptes Rendus, Nov. 17, 1851. 



On the Transmigration of Worms. By Chari.es Vogt. 



The worms, those Pariahs of the animal kingdom, have long been 

 neglected by zoologists ; the intestinal worms in particular, from the 

 uncertainty which existed as to their organization and development, 

 have been united into an ill-defined group. It is nevertheless amongst 

 these animals that modern zoology has discovered some of the most re- 

 markable facts in the history of the animal organism and embryogeny. 



The theory of spontaneous generation, attacked and overturned on 

 all sides, has long sought a last refuge in the history of the intestinal 

 worms. How has it been possible for an animal, a parasitic worm, de- 

 prived of sexual organs, to appear and propagate in the closed cavi- 

 ties of the bodies of man or animals? Such is the embarrassing 

 question put by the partisan of the " generatio cequivoca" If we 

 dissect one of our little freshwater fishes, the stickleback (Gaste- 

 rosteus aculeatus), we shall find in the cavity of its body a worm be- 

 longing to the genus Bothriocephalus, which is entirely destitute of 

 generative organs. If we confine ourselves to this single fact, the 

 formation and reproduction of this parasite are no doubt difficult to 

 explain, and one is easily tempted to call in the aid of the Deus ex 

 machind of spontaneous generation. But a second observation shows 

 us, that at the moment when the fish in question becomes the prey of 

 some aquatic bird, its worm passes into the body of its destroyer, 

 where it receives its true development, — for it is then only that its 

 segments become filled with eggs, which, rejected with the excre- 

 ments of the bird, fall into the water and thus pass into the bodies of 

 the fishes which swallow these excrements. Without pretending to 

 explain the history of all the parasitic worms as naturally as this, we 

 present the following facts as a new argument against their pretended 

 spontaneous generation. 



All worms possess generative organs, provided they find the con- 

 ditions necessary for their development. It is true that we find in 

 worms, Crustacea, Insects, &c, parasites, called Gregarince, totally 



