ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 937 



future dorsal lip of the blastopore, it becomes deflected downwards 

 and continuous with the axial strip of the lower-layer-cells. In the 

 more lateral parts the ectoblast continues to be differentiated and the 

 cells meet again in the middle line a little way behind the blasto- 

 pore. 



Discussing the results of their observations, they point out that 

 the agreement between the development of Amphioxus and the 

 Amphibia on the one hand, and the Reptilia on the other, is as com- 

 plete as could be desired, due allowance being made for the necessary 

 differences between holoblastic and meroblastic eggs ; their studies 

 confirm the conclusions of Hertwig, while they contradict the views 

 of Strahl, who has opposed Hertwig. 



Oleaginous Spheres in the Ova of Teleostean Fishes. * — Mr. 

 E. E. Prince thinks that there is little value in the division of pelagic 

 eggs into those with one or more oil-globules, and those that are not 

 so distinguished, which has been suggested by Messrs. Agassiz and 

 Whitman ; the ova of closely allied species exhibit the utmost 

 diversity in this respect. Most Gadoid ova are, for example, without 

 the spheres, but in the ling (Molva vulgaris) there is a single 

 oleaginous sphere of a pale green tint. The spheres may be trans- 

 ferred from one region of the yolk to another, but the normal position 

 is at the vegetal pole, and thither they always return when the 

 rotated yolk comes to rest. The precise chemical nature of these 

 large globules is still uncertain, but their composition appears to be 

 allied to the lecithin derivates of albumin. It is possible, therefore, 

 that they have an ancestral significance ; the yolk matter of the 

 Teleostean ovum was, Balfour thought, once greater in bulk than it 

 is now, and if, as the vitelline mass diminished, the lecithin did not 

 decrease in the same degree, globules would be formed such as are 

 found in so many Teleostean eggs. 



Embryology of the Opossum.f— Prof. E. Selenka communicates 

 a short report on the develojmient of the opossum, and origin of the 

 mammalia. After segmentation has ended, the egg consists, from 

 outside inwards, of a zona radiata, a layer of nutritive yolk, the 

 ectoderm, the endoderm, and the yolk-cavity. From the primitive 

 groove, an anterior proliferation forms the chorda dorsalis, the two 

 mesoderm folds are formed at the sides. Five days after fertilization 

 the amniotic duct is closed. There is no transitory ectoderm, and no 

 formation of villi. The nutrition of the embryo is effected solely 

 by the osmosis of uterine lymph through the chorion. The very 

 loose attachment of the egg is effected by the persisting zona. The 

 nuclei of the strij)ed muscle fibres lie axially. 



r Structure and Development of Feathers.J — Dr. E. Klee gives a 

 useful account, supplemented and corrected by his own observations 

 of what is known in regard to the structure and development of 



* Ann. and Mag. Nat. Hist., xviii. (188G) pp. 84-90. 



t Biol. Ceutralbl., vi. (1SS6) pp. 2S3-4 (Bericht Versarnml. Deutsch. Naturf., 

 StrassbuTg, 1885). 



\ Zeitschr. f. Naturwiss., lix. (188G) pp. 110-56 (1 p].). 



