Royal Society . 385 



in the year 1 792. The name of Ornithorhynchus, which it at present 

 bears, was given to it by Blumenbach ; and some account of the 

 structure of the head and beak was given in the Philosophical Trans- 

 actions by Sir Everard Home in 1800 ; and in a subsequent paper he 

 Slates his opinion that this animal difiers considerably from the 

 true mammalia in its mode of generation, an opinion which was 

 adopted by Professor Geoffroy St. Hilaire, who accordingly placed 

 it, together with the Echidna, in a separate order designated by the 

 term Monotremes. He afterwards formed this group into a distinct 

 class of animals, intermediate to mammalia, birds, and reptiles. Oken 

 and De Blainviile, on the other hand, condemned this separation j 

 aiid maintained that the monotremata should be ranked among mam- 

 malia, and as being closely allied to the marsupialia ; and hazarded 

 the conjecture that they possessed mammary glands, which they ex- 

 pected would ere long be discovered. Professor Meckel has since 

 described these glands as being largely developed in the female 

 Ornithorhynchus. He considers this animal, however, in the mode of 

 its generation, as making a still nearer approach to birds and rep- 

 tiles, than the marsupial tribe. He was unable to inject these glands 

 in consequence of the contracted state of the ducts arising from the 

 action of the spirit in which the specimen was preserved, and from 

 their being filled with a concrete matter. Geofl'roy St. Hilaire, in a 

 subsequent memoir, persists in denying that these bodies possess the 

 characters of mammary glands ; but regards them as a collection, not 

 of acini, but of caeca, having only two excretory orifices, and present- 

 ing no trace of nipples. 



The author of the present memoir, having examined with great 

 care the specimens of the female Ornithorhynchus preserved in the 

 Museum of the Royul College of Surgeons, found the structure to 

 correspond very exactly with the account given by Meckel; and, 

 moreover, succeeded in injecting the ducts of these glands with mer- 

 cury. He further notices the differences of development occurring in 

 five different specimens: the size of these glands having an obvious 

 and direct relation to that of the ovaria and uteri. The gland itself 

 is composed of from 150 to 200 elongated subcylindrical lobes, dis- 

 posed in an oblong flattened mass, converging to a small oval areola 

 in the abdominal integument, situated between three and four inches 

 from the cloaca, and about one inch from the mesial line. It is si- 

 tuated on the interior of the panniculus carnosus, the fibres of which 

 separate for the passage of the d\icts to the areola ; the orifices of 

 these ducts are all of ecjual size, and occupy an oval space five lines 

 in length by three in breadth ; not elevated however in the slightest 

 degree aljove the surrounding integument. An oily fluid may be 

 expressed from the ducts by scjueezing the gland. 



A minute description is tlicn given of theaniitomical structure of the 

 internal genito-urinarv organs of the female Ornithorhynchus: from 

 which it ajjpears that if the animal be oviparous, its eggs must, from 

 the narrow space through which they have to pass in order to get out 

 of the |)elvis, be smaller than those of a sparrow j and no provision 

 appears to he made for the addition of albumen or of shell in the 



T/iinl Said. Vol. 1. No. 5. Nuv. 18^2. 3 D 



