156 Miscellaneous . 



MISCELLANEOUS. 



On the Embryogeny mid Propagation of Intestinal Worms. By 



MM. Ercolani and Vella. Abstract by Prince .Charles 



Bonaparte. 

 The recent investigations of German naturalists on the propaga- 

 tion and metamorphoses of the Cestoid worms have ah-eady engaged 

 the attention of the Academy, but our authors have occupied them- 

 selves with the same phsenomena in the Nematoid worms, of which 

 we know scarcely anything. 



After combating the most specious arguments that have been 

 advanced in favour of the doctrine of heterogeny, they endeavour to 

 show by simple and clearly stated facts, that, in spite of the general 

 opinion, the Entozoa enjoy a marvellous tenacity of life. To such 

 an extent does this go, in fact, that their embryos have lived six 

 days immersed in alcohol, and been revived after thirty days of com- 

 plete dryness. 



The embryogeny of the Ascaris megalocephala of the horse, hitherto 

 scarcely known, appears to be almost completely elaborated. The 

 artificial development of this worm was effected by Dr. Ercolani in 

 the lung of a dog. The description of these experiments is followed 

 by some new observations in comparative embryogeny relating to the 

 Graafian vesicle, the formation of the chorion and of the vitelline 

 membrane, and especially to the successive development of the organic 

 constituents of the worms. 



Lastly, he shows how the ova of the Nematoids, after passing into 

 the bodies of animals with their food, insinuate themselves into the 

 walls of the intestine, so that their presence completely escapes de- 

 tection. In this position these ova undergo a sort of incubation, and 

 the embryo becomes sufficiently developed to return into the intestinal 

 cavity, where it is afterwards to pass its life. 



In concluding their memoir the authors give the following resume 

 of their facts : — 



1 . " The progressive metamorphoses of the Entozoa, hitherto 

 studied by Van Beneden, Kiichenmeister and Siebold, although re- 

 vealing to us new and astonishing facts, are not applicable to the 

 entire solution of the questions connected with the genesis of all 

 Entozoa. 



2. ** Although the retrogressive metamorphosis of the ova of Tcenice 

 into Cysticerci and Coenuri have not succeeded with the authors as 

 with some other observers, they have nevertheless led them to re- 

 cognize a lower phase in the development of the Cysticercus cuniculiy 

 a phase which approaches this worm to the lowest and most simple 

 worms : although they present an invaginated head, they are destitute 

 of the small openings, the hooks, and the caudal vesicle, so that the 

 opinion entertained by some that the Cysticerci are degenerated 

 TcenicB is not well founded. 



3. "The Nematoid worms do not undergo anything like a pro- 

 gressive metamorphosis ; the changes observable in the embryo are 



