ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 441 



tissue and even with the spleen. The islands of Langerhans arise very 

 early as a solid mass of epithelial tissue which becomes broken up by the 

 splitting of the mesenteric artery. 



There are certain features which suggest an earlier condition of 

 Teleostean evolution than is the case with other Teleosts whose develop- 

 ment is known. Assheton inquires speculatively whether the Teleosteans 

 may be descended from a proto-amphibian stock, which by a mutation 

 returned to strictly aquatic habits. He refers to the amphibian-like 

 character of the lips of the blastopore, to the vestige of neural tube 

 formation, to various features in the development of the excretory 

 system, to the lung-like and vestigially double air-bladder, to the trace 

 of an auricular septum and the suggestion of a double circulation, to the 

 large size of the aortic arch of the fourth visceral arch, and to the 

 peculiar character of the gill-clefts, filaments and arches. 



Regeneration in the Pancreas.* — J. Kyrle has experimented with 

 dogs and guinea-pigs, and finds that the pancreas has some regenerative 

 capacity both as regards the parenchyma and the islands of Langerhans. 

 From their own epithelial components both these kinds of tissue may 

 effect regeneration, but this may be supplemented by re-growth from the 

 efferent ducts. 



Early Human Embryo.f — Alexander Low describes a human 

 embryo of 13-14 mesodermic somites, 2' 6 mm. in length. He has 

 reconstructed a model of the whole and of various parts. The noto- 

 chord lies in close relation with the endoderm forming the roof of the 

 gut, and is not separated off at its cranial commencement, appearing 

 more as a heaping up of cells than as an evagination. The aortic stem 

 divides into a pair of aortic arch vessels, and there are traces of a second 

 pair. The dorsal aorta is paired throughout. The mouth, which is 

 separated from the pharynx by a complete bucco-pharyngeal membrane, 

 shows on its roof a slight funnel-like beginning of the oral part of the 

 hypophysis ; the pharynx shows four pairs of pouches. The medullary 

 plate is still open at both ends ; the hind brain shows seven neuromeres. 



Corpus luteum and Rut in Rabbits.J — CI. Regaud and G. Dubreuil 

 have made experiments which they regard as proving that the corpora 

 lutea do not condition rut. But F. Vuillemin,§ whose results are criti- 

 cised by Regaud and Dubreuil, maintains his previous conclusion that, in 

 the rabbit, as in other mammals, rut (like menstruation) is determined 

 by the internal secretion of the cells of the corpus luteum. 



Open Cleft in Embryonic Eye of a Chick of Eight Days. || — 

 Otto Landman found a case in which the fissure, which normally closes 

 on the 6th day, was widely open on the 8th day. A complete cleft 

 extended from the edge of the pupil to the region of the optic nerve ; 

 there was an inversion of the lips of the foetal cleft throughout its 



* Arch. Mikr. Anat., lxxii. (1908) pp. 141-60 (1 pi.). 



t Journ. Anat. Physiol., xlii. pp. 237-51 (3 pis. and 15 figs.). 



X C R. Soc. Biol. Paris, lxiv. (1908) pp. 142-4. 



§ Tom. oit., pp. 444-5. 



|| Anat. Anzeig., xxxii. (1907) pp. 456-9 (5 figs.). 



