ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 133 



taryokinesis, but the two daughter-cells remain together in the region 

 corresponding to the equator of the division-spindle. The mitosis 

 appears to occur very rapidly, for it is difficult to catch many cells in the 

 process. ' J. A. T. 



c. Greneral. 



Aqueous Humour. — ^y. A. Osborne {Journ. Physiol., 1919, 52, 

 317-50.) The aqueous humour presents the singular phenomenon of a 

 body fluid surrounded by living tissue, and yet containing so little protein 

 that it may be regarded as practically protein-free. The chief solids in 

 it are metallic salts. But the common statement that the aqueous 

 humour has a higher osmotic pressure than the blood is challenged. In 

 fact, it is found that the osmotic pressure of ox aqueous humour is 

 equal to that of blood. Other quantitative considerations support the 

 view that the humour is a blood filtrate. The osmotic pressure of the 

 blood proteins in the iridic vessels will cause absorption of aqueous 

 humour if the excess pressure in these vessels is less than 30 mm. Hg. 



J. A. T. 



Moult and Regeneration of Pelage in Deer-mice. — H. H. Collinj? 

 {Journ. Exper. Zool., 1918, 27, 73-99, 2 pis.). In Peromyscus the 

 moulting is, in a measure, comparable in regularity of sequence and 

 directions of growth to the moults of birds. In the post-juvenal moult, 

 growth occurs more or less independently on certain regions of the 

 body, suggesting the mode of moult in the feather tracts of birds. In 

 adults the moults are generally more irregular and inconspicuous. By 

 plucking out juvenal hair, the precocious appearance of the post-juvenal 

 pelage may be induced, and this is sometimes preceded by the out-growth 

 of an' aberrant type of hair, with abnormal pigmentation, which persists 

 only for a short time. The normal sequence of the incoming hair is 

 profoundly modified by artificially induced regeneration. Restoration 

 of pelage in adults occurs irrespective of the season, after the plucking 

 out or clipping of the old hair. This restoration is accomplished by the 

 outgrowth of new hairs, except in the case of the vibrissa, which are 

 replaced by the elongation of the cut hairs. Restoration is much more 

 rapid when the hairs are plucked out than when merely cut. Light 

 appears to be a negligible factor in the development of the differential 

 coloration of the dorsal and ventral surfaces. J. A. T. 



New Mendelian Variety of Norway Rat. — P. W. Whiting and 

 Helen Dean King {Journ. Exper. Zool, 1918, 26, 55-04). A new 

 Mendelian variety, known as ruby-eyed dilute grey, has been found near 

 the Zoological Laboratory of the University of Pennsylvania. The hair 

 is Ught sepia at the tip and grades to white at the base. The eye- 

 colour is ruby. The new variation is recessive to intense pigmentation. 

 Ruby-eyed dilution is allelomorphic with albinism. The F^ individuals, 

 called fawns, are intermediate both in hair and in eye-colour. Fawns 

 when bred together i")roduced eighty ruby-eyed dilutes, one hundred and 

 fifty-six fawns, and eighty albinos. Ruby-eyed dilutes crossed witli 

 red-eyed yellow rats produce rats of the wild type. J. A. T. 



