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ings. He gives in each case a particular account of the mode of 
dissection, with a view to direct succeeding observers to obtain a 
distinct view of the parts he describes, and to verify the conclusions 
he has himself obtained. 

He next notices a considerable modification in the structure of 
these organs which is presented in the Chiton. In this animal he 
linds a pair of simple lateral jaws, rather membranous than cartila- 
ginous. Another variety of structure adapted for gorging food is 
met with in the Patella mammillaris, where there is simply a very 
muscular mouth and pharynx, but neither cartilage, tongue^ nor 
hard part of any kind. 

The apparatus by which the Bitccinum Lapillus drills through shells 
in order to obtain its food, and the process it employs for that pur- 
pose, are next investigated -, and that of the Buccinum undatum is 
particularly examined with the same view, the structure of the latter 
being very fully displayed. 

The author hopes to be enabled to pursue these inquiries with 
respect to other tribes of Mollusca at some future period. 

6. ^^ On the Mammary Glands of the Ornithorhynchus paradoxus,^^ 
by Richard Owen, Esq. Communicated by J. H. Green, Esq, F.R.S. 

The author premises a history of the different opinions that have 
been entertained with respect to the anatomy and economy of this 
singular animal, which was first described and figured by Dr. Shaw 
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 5 and in a subsequent paper he 
states his opinion that this animal differs 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 Blainville, on the other hand, condemned this separation -, 
and 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. Geoftroy St. Hilaire, in a 
subsequent memior, persists in denying that these bodies possess the 
characters of mammary glands 3 but regards them as a collection, not 
of acini, but of cseca, 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 Royal College of Surgeons, found the structure to 
correspond very exactly with the account given by Meckel j 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 ducts to the areola j the orifices of 
these ducts are all of equal size, and occupy an oval space five lines 
in length by three in breadth ; not elevated however in the slightest 
degree above the surrounding integument. An oily fluid may be 
expressed from the ducts by squeezing the gland. 

A minute description is then given of the anatomical structure of the 
internal genito-urinary organs of the female Ornithorhynchus : from 
which it appears 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 pelvis, be smaller than those of a sparrow j and no provision 
appears to be made for the addition of albumen or of shell in the 
structure of that part of the canal through which they afterwards 
descend previous to their expulsion from the body. The ova are en- 
veloped in a tough fibrous membrane in which the traces of vascu- 
larity, at least after being preserved in spirits, are not perceptible j 
whilst in birds the ova are attached by narrow pedicles, and are co- 
vered by a thin and highly vascular membrane. 

From the whole of this inquiry, the author concludes that these 
glands are not adapted to the performance of any constant office in 
the economy of the individual, but relate to a temporary function. 
Their total absence, or at least their rudimentary condition, in the 
male, of which the author could perceive some traces in one speci- 
men which he examined, and the greater analogy of their structure 
to a lacteal apparatus than to that of ordinary odoriferous glands, 
when taken in conjunction with the correspondence of their deve- 
lopment to that of the uterine system, induce him to believe that they 
are to be regarded as real mammae. This view is confirmed by the 
fact, noticed by Mr. Allan Cunningham, that the young of this animal 
readily takes cow's milk, and may be kept alive by this kind of sus- 

7. ''A Physiological Inquiry into the Uses of the Thymus Gland," 
by John Tuson, Esq. Communicated by J. C. Carpue, Esq. F.R.S. 

The author is of opinion that the thymus gland is intended for two 
purposes : the one to serve as a receptacle of blood for supplying 
the chasm in the circulation occasioned by the great quantity sent 
to the lungs as soon as the function of respiration commences : the 
other to serve as a receptacle of osseous matter preparatory to the 
extensive ossification which is carried on in the early periods of