MAMMALIA. 711 



only indicated by the convergence of a few wrinkles to one point ; 

 but, when these were put upon the stretch, the integument was 

 found entire, and completely shrouding or covering the eye-ball 

 anteriorly : its skeleton was, moreover, quite in a cartilaginous 

 condition, and it was obviously in every respect helpless, and still 

 dependent upon its mother for sustenance. 



The stomach was found filled with milk, a sufficient proof that 

 at that period, at least, it was nourished by the lacteal secretion ; 

 but, with regard to its previous fetal condition, the difficulties that 

 have been above alluded to remained in their full force. No trace 

 of an umbilical cicatrix was visible upon the ventral surface of the 

 body, even when examined with a lens, a sure proof that no pla- 

 centa had existed. The ileum was carefully examined, but there 

 was no appearance of the pedicle of the vitelline vesicle ; neverthe- 

 less, the other vestiges of fetal organization were more obvious 

 than in the ordinary marsupial or ovo-viviparous Mammalia. The 

 umbilical vein was seen extending from a linear cicatrix of the 

 peritoneum, opposite the middle of the abdomen, along the ante- 

 rior margin of the suspensory ligament to the liver. It was re- 

 duced to a mere filamentary tube filled with coagulum. From the 

 same cicatrix the remains of the umbilical arteries extended down- 

 wards, and near the urinary bladder were contained within a dupli- 

 cature of peritoneum, having between them a small flat oval vesicle, 

 the remains of an allantois, which was attached by a contracted 

 pedicle to the fundus of the bladder ; but still as both the em- 

 bryo of a Bird and that of the ovo-viviparous Reptile have an 

 allantois and umbilical vessels developed, no certain inference can 

 be drawn from the above appearances as to the oviparous or vivi- 

 parous nature of the generation of the Ornithorynchus. 



(836.) Such is the present state of our knowledge relative to 

 the first type of Mammiferous generation, viz. that met with 

 among the MONOTREMATA. In the second, or MARSUPIAL 

 TYPE, the phenomena, although equally strange, are better under- 

 stood, and to these we must now beg the attention of the student. 



The MARSUPIALIA, from the variety of their forms and exten- 

 sive distribution, constitute a most important section of Mammi- 

 ferous quadrupeds, distinguished by the peculiarities that occur in 

 the organization of their generative apparatus, and by the singular 

 mode in which they produce and suckle their young. Animals of 

 this kind are only met with in the American and Australian 

 regions of our globe ; and so widely do they differ, as far as their 



