194 Professor OwerCs Reply 



in the formation of the placenta, is developed at a much 

 earlier period than in the birds ; at an epoch to which the 

 vague term, primordiale, may perhaps be applied, but which 

 I shall more distinctly define by stating, that in the embryo 

 of the rat, for example, the allantois makes its appearance 

 before the head is distinguished from the body by any cervi- 

 cal constriction, before the complete elimination of the intes- 

 tinal tube, and before the appearance of the extremities : the 

 abdomen is also widely open. In the embryo calf, the two- 

 horned allantois makes its appearance at a still earlier period. 



Now the importance to physiology of examinations of the 

 marsupial ova chiefly depends on the impartiality of the ob- 

 server, on the independence of his mind from preconceived 

 notions of the analogies which the marsupial ova ought to 

 present to the higher mammiferous, or to any other class of 

 ova. Descriptions/row? induction are above all to be scouted 

 in reference to these rare and difficult subjects of embryolo- 

 gical research. It is through the marsupial ova that we shall 

 obtain the key to the true nature of the modifications of the 

 ova of the placentally developed Mammalia, and these marsu- 

 pial ova, if fairly and rightly studied, will teach us what are 

 the oological conditions and phenomena which essentially 

 relate to the developement of a placenta. 



What an example of an investigator of scientific truth does 

 M. Coste present to our eyes, when he infers that the embryo 

 of the kangaroo, at a certain period of developement must 

 have possessed an allantois, because the placental embryo 

 at the same, or at an earlier period, manifests this appendage ! 

 An inference moreover which he had once the opportunity of 

 confirming or rejecting, from actual observation, and which 

 he now puts forth merely to throw discredit on the unbias- 

 sed researches of the individual who had exerted his utmost 

 to improve M. Coste' s knowledge on this branch of embryology. 

 M. Coste, in the same spirit, makes an assertion which is not 

 consistent with fact, and for which he has no foundation : he 

 says that the marsupial uterine foetus first described by me, 

 was 'deja parfaitement developpe, 7 and that Tevasement abdo- 

 minal avoit completement disparu." Now the specimen itself, 

 which M. Coste saw, and my description and figures thereof, 

 equally contradict these assertions. I have particularly no- 

 ticed at p. 37, of my Memoir of 1834, that the abdominal pa- 

 rietes were not completed, and that a loop of intestine was 

 out of the abdomen, and contained in the short umbilical 

 chord; and I have figured this condition of the uterine/a?- 

 tus zXfig. 3, pi. vii. 



I moreover took the pains, after having ascertained the con- 



