1819.] Royal Society. £>\ 



ova of the opossum tribe. After alluding to the formation of 

 the ova of quadrupeds, as described by him on a former occasion, 

 the author proceeded to the subject of his present paper. The 

 ova of the opossum tribe are formed differently from the ova of 

 quadrupeds, and constitute two distinct gradations between that 

 class of animals and the ornithorhynchus paradoxus, which last 

 approaches so near the bird as to complete the series between 

 quadrupeds and birds. The formation of an ovum in the kanga- 

 roo was first described. This, when expelled from the corpus 

 luteum, receives a yolk in the fallopian tube, and subsequently 

 an albumen in the uterus. The foetus, when removed t'rom the. 

 uterus into the marsupium, attaches itself to the nipple as for- 

 merly described.* In the wombat, and the great and small 

 opossum, instead of corpora lutea, yolk bags are imbedded in the 

 substance of the ovarium, and there are two uteri with a fallopian 

 tube to each, the ovum in each uterus being separately impregr 

 nated in its own cavity. The mode of formation of the ova in the, 

 ornithorhynchus paradoxus constitutes the intermediate link 

 between the opossum and bird. In this animal, the yolk bags 

 are imbedded in the ovana, and instead of a regular uterus, each 

 fallopian tube swells out into a cavity in. which the ova are 

 impregnated. 



A paper was read, by J. F. Wood, Esq. entitled " A Case of 

 a Blue Child, with the Dissection." This child lived 21 months, 

 On removing the pencaidium after death, a large vein was 

 observed descending on the left side of the thorax, and terminate 

 ing in the right auricle of the heart, in which the superior vena 

 cava also terminated by a distinct opening. The auricle was. 

 large, and the foramen ovale pervious. The aorta and pulmonary 

 artery arose from the right ventricle, the cavity of winch was 

 likewise large and strong, and had no communication with the 

 left, except by a foramen through the septum, which divides the 

 ventricles. Such were the chief peculiarities observed in this 

 case, which were illustrated by drawings. 



There was likewise read at this meeting, a paper, by W. Mor- 

 gan, Esq. entitled " Observations on the new System of diagonal 

 Framing, introduced into his Majesty's Navy by It. Seppings, 

 Esq." After some general observations upon other suggested 

 improvements, the author proceeded to state his reasons for pre- 

 ferring Mr. Seppiugs's principles, and to point out the advantages 

 arising from their adoption. The paper was accompanied by 

 drawings illustrative of the subject. 



April 29. — A paper, by Dr. Brewster, was commenced, on 

 the optical and physical properties of tabasheer. 



May rj. — Dr. Brewster's paper was concluded. After men- 

 tioning the mode of formation and chemical properties of taba- 

 sheer, Dr. B. proceeded to state that there are three varieties of 

 this substance ; one possesses a milky transparency, and reflects 



• See Pbil. Trans, vol.lyxxv. nud c. 



o2 



