Zoological Society. 63 



of the known structure: 2ndly, Externally, an apparatus formed of 

 ceeca, furnished with some membranous and diaphragmatic/ra «a, and 

 with many cellulosities. This apparatus, in the young state and during 

 the inactivity of the sexual organ, consists only of a longitudinal projec- 

 tion without distinct characters ; but during the season of sexual ex- 

 citement, this projection becomes enlarged and is visibly surmounted 

 on its internal surface by a multitude of small parallel cceca, dissemi- 

 nated over and attached to the glandular body, like the bristles upon 

 a brush. These cceca open on the projection made by the gland, which 

 on its tegumentary surface has but a single excretory orifice. The 

 secretion consists of a mucus possessing a very powerful odour. 

 * * * * * " * 



" The epigastric artery is divided into two principal branches ; one 

 passing towards the median line to supply the mammary glands ; the 

 other ramifying externally and performing the same function with re- 

 gard to the odoriferous glands. The same structure exactlyis presented 

 by the ventral glands of the Ornithorhynchus, two characters excepted, 

 which do not militate against the determination and analogy assigned 

 to them : viz. a much more extensive development, and two secretory 

 orifices instead of one, as in the Shrews. I explain this difference by 

 the atrophy and entire suppression of the internal epigastric branch. 

 This branch being annihilated, there is no formative vessel, and con- 

 sequently no apparatus produced, — no mammary gland ; but, on the 

 other hand, the whole arterial alimentation passing more excentrically 

 by means of the single terminal branch, the apparatus to which this 

 branch is distributed is proportionally enlarged. This shows why and 

 how the odoriferous glands have reached, in the Monotremata, their 

 maximum of development. Where the apparatus becomes more con- 

 siderable, the function is so much the more powerful, and the mucus 

 secreted must in fact exist in such quantity in the Monotremata, that 

 its effusion may become a fact susceptible of observation. 



" I should not be surprised, if this mucus, more abundant and more 

 substantial in the Monotremata, became the nutriment of the young 

 after their hatching. The Monotremata would act, in this respect, 

 like some aquatic birds which conduct their young after hatching to 

 the water, and assist them in their substantation. The maternal in- 

 stinct would lead the female Ornithorhynchus to effect the contraction 

 of the gland, which is possible by the efforts of thepanniculus carnosus 

 and the great oblique muscle, between the fibres of which the gland is 

 seated, and thus to procure for the young, at several periods of the day, 

 by way of nutriment, an abundant supply of mucus. If this education is 

 carried on in the water, where we know, by the history of the generation 

 of frogs and the nutrition of their tadpoles, that the mucus combines 

 with the ambient medium, becomes thick, and supplies an excellent 

 nutriment for the early age of these reptiles, we shall understand the 

 utility of the ventral glands of the Ornithorhynchus, as furnishing a 

 source of nutriment for the young of these animals, — for young ovipara 

 newly hatched. When we meet with such curious organic conditions, 

 we do not attempt, by a truly retrograde march, to throw back well 

 averred differential facts, decidedly acquired to science, by means of 



