ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 25 



the cycle is longer, 9 to 17 days. The cycles following unfertile copu- 

 lations are usually 10 to 19 days. Stimulation of the cervix uteri by 

 inserting a glass rod in the first oestrus stage prolongs the next cycle to 

 11 to 19 days ! Perhaps the vaginal plug acts in this mechanical way. 



J. A. T. 



Wound Healing in Early Embryo of Chick.— C. W. M. Poynter 

 {Anat. Record, 1919, 16, 1-23, 12 figs.). Wounds of the chick's blasto- 

 derm heal with great facility, and the process can be watched for a 

 number of hours in hanging-drop preparations. In wounds of the 

 €xtra-embryonic blastoderm all the three germinal layers take part in 

 the process, but the ectoderm and endoderm are somewhat more active 

 than the mesoderm. There is de-differentiation, fusion of cells, and re- 

 differentiation. Wounds of the embryo itself heal by de-differentiation 

 of the ectodermal epithelium and the amoiljoid migration of these cells 

 over the cicatrix. There is no regeneration of the underlying parts, and 

 the endoderm takes very little part. The migration is probably chemico- 

 physical ; the covering of the wound is effected without the occurrence 

 of 'cell proliferation. It would seem that wound repair is a step or 

 phase of the process of regeneration, and that the embryonic dominance 

 is so pronounced that it prevents the wound stimulus from carrying the 

 process beyond this phase. J. A. T. 



Post-mortem Melanin Formation in Eyes of White Ring Doves. 

 — OscAK Riddle and Victor K. La Mer {Amer. Journ. Fhyaiol., 



1918, 47, 103-23). In the retina-choroids of white dove embryos of 

 three to twelve days of development, melanin was formed after death. 

 The pigment is not produced in earlier stages, and is not as readily pro- 

 duced, if at all, in the full-term or just-hatched embryos. Killing the 

 tissues in HgClo does not prevent the development of the pigment, but 

 the development of free oxygen is necessary in percentages varying 

 between that present in air and 100 p.c. The pigment fails absolutely 

 to form in an atmosphere of CO^,. It seems probable that the inner 

 ring of iridial pigment disappears when kept after death in the presence ■ 

 of high percentages of COo. The facts oi post-77iortem melanin formation 

 have a bearing on current theories of colour inheritance and develop- 

 ment. They coincide with the view advanced by Riddle in 1909 

 {Biol. Bulletin, 1909, 16, 316), and present difficulties and limitations 

 to the " presence and absence " hypothesis of colour development. 



J.A.T 



Brachydactyly in Fowl. — C. H. Danforth (Amer. Journ. Anat., 



1919, 25, 97-115, 5 figs.). In certain strains of poultry (and probably 

 in pigeons) there is a close correlation between brachydactyly involving 

 the size and number of bones in the feet, and the presence of feathers 

 on the tarsi. While the size and number of skeletal elements are 

 determined by the length of the embryonic toe, there is no causal relation 

 between toe-length and feathering. The data seem rather to suggest 

 that brachydactyly, feathering of the tarsi, and probably syndactyly, are 

 .all dependent on one and the same factor, the nature of which is obscure. 

 It is suggested that a study of the early functioning of the endocrine 



