MR. OWEN ON THE GENERATION OF THE MARSUPIAL ANIMALS. 361 



It is interesting to find these analogies to the Reptilia ; and more might be pointed 

 out if it were not a comparison which merits a separate consideration, and would 

 extend the present communication to an undue length. 



There is, however, another order of Mammalia which, in addition to certain ana- 

 logies to the Reptilia manifested in their generative and other systems, have the brain 

 nearly as simple as in the Opossums : these are the Edentate Mammalia ; and the Ar- 

 madillos, Manises, and Anteaters are more especially characterized by their inferiority 

 in this respect, the Sloths, like the Kangaroo, having a few superficial anfractuosities 

 on the cerebral hemispheres. In order, therefore, to test the degree of relationship 

 which exists between a long intra-uterine and placental development, and the perfec- 

 tion of the brain, it will be requisite to possess an accurate knowledge of the mode 

 of development of the above Edentate genera. 



This is an inquiry well deserving attention ; and it is to be hoped that the desirable 

 materials, viz. the impregnated uteri of the Edentate and Marsupiate genera, will soon 

 be furnished through the exertions of our scientific countrymen abroad. 



Description of the Vlates. 



Plate VI. 



Fig. 1. Communication of the true vagina with the urethro-sexual passage by a 

 double orifice, resulting from an occasional formation of the hymen, in 

 the Human subject. 

 Fig. 2. A section of the urethro-sexual canal, showing a similar mode of communi- 

 cation by a double orifice, resulting from a constant formation of the 

 hymen, in the Sow. 

 Fig. 3. A similar section of the urethro-sexual passage of the Kangaroo. 



In each of the figures, a is the urethral, and b h the vaginal orifices. 

 Fig. 4. The female organs of an Armadillo (Dasypus novem-cinctus, Linn.). 

 Fig. 5. The female organs of the Merian Opossum (Didelphys dorsigera, Linn.), 



magnified three diameters. 

 Fig. 6. The female organs oFthe Kangaroo Rat {Hypsiprymmis fVhitei, Lesson). 

 The same letters indicate the same parts in each of the figures. 

 a. Ovaries. 



h. Fallopian tubes. (In figg. 5. and 6. Membranous portion of the Fallopian 

 tubes, Home.) 



c. Uteri. {Cornua uteri, Tyson, Daubenton. In figg. 5. and 6. Glandular por- 



tions of the Fallopian tubes, Home ; Aduterums, Geoffroy.) 



d. Os tincee. (In figg. 5. and 6. Valvular termination of Fallopian tube, Home.) 

 €. Mesial cul de sac of the vagina. {Corpus uteri, Tyson, Daubenton, Geof- 

 froy ; Uterus, Home.) e, e. Divided portion of the vagina. {Uteri re- 



