ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 35 



result of sexual intercourse. Since coition and ovulation take place 

 lifter the pro-oestrum, it is clear that the degeneration stages of the pro- 

 ■cestrum cannot be of the nature of an undoing, in consequence of the 

 absence of a fertilised ovum, of preparations made during the earlier 

 growth stages. 



Implantation of Ovum in the Gopher.* — T. G. Lee gives an 

 account of the fixation of the ovum in this rodent (Spermophilus 

 tridecemlineatus), which differs from its relatives, and, further, from 

 any other mammals yet described in the nature and history of the 

 temporary "fixation-mass " formed by the trophoblast. 



Development of Pulmonary Arteries in Roe-deer. f — T. Sakurai 

 finds that the pulmonary arteries arise first from both pulmonary arches 

 as in man, but gradually the left passes over to the right pulmonary 

 arch approaching the right artery. The portion of the right pulmonary 

 arch between the angle of division of the arches and the origin of 

 the left pulmonary artery forms the common origin of both pulmonary 

 arteries. 



Development of Mammalian Kidney .% — J. Janosik has investigated 

 certain early stages of the urogenital system in the pouched marmot. 

 He finds the first certain appearance in embryos with ten distinct and 

 one incipient mesoblastic somites. It arises opposite the seventh somite 

 proximally as a grouping of somatopleure and splanchnopleure cells 

 against the somites ; the ccelome is slightly indented into this group. 

 The section situated between the twelfth and fifteenth or sixteenth 

 somites in embryos showing these, is regarded as transitional to the 

 mesonephros. The origin of this division of the mesonephros takes 

 place as follows. The middle plates detach themselves both from the 

 mesoblastic somites and from the ccelomic epithelium, and from them 

 there arises a cellular strand which falls into separate cell masses not 

 segmentary arranged. In these cell masses a lumen arises, which is 

 transformed into a vesicle from which a small canal grows out. On the 

 median end of each of these canals a glomerulus is formed, while the 

 lateral end opens into the Wolffian duct. Thus connections arise similar 

 to those known to occur in birds. 



Regeneration of Tail-tissues in Anuran Larvae. § — P. Wintrebert 

 gives the results of experiments on the larva of Alytes. He finds that 

 regeneration of the tail depends upon the reconstitution of the sup- 

 porting apparatus, more especially the axis of central support round 

 which the embryonic mesenchyme can be organised. The median 

 " lophiodermic raphe " of the limbs constitutes a sufficient apparatus 

 of support to admit of the regeneration of the cord. The connective 

 fibrous neural and aortic canals are powerless, with the organs they 

 inclose, to supply the place of the missing cord or to regenerate it. 

 They may in fact by their re-union oppose its extension and thus limit 



* Mark Anuiv. Vol., 1903, pp. 417-35 (2 pis.}, 

 t Anat. Anzei-., xxv.(1904) pp. 321-6. 

 t Arch. Mikr. Anat., lxiv. pp. 214-34 (2 pis.). 

 § Comptee Rendus. cxxxix. (1904) pp. 432-4. 



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