286 SUMMARY OF CURRENT RESEARCHES RELATING TO 



arise as evaginations from the same part of the mesoderm. Three types 

 of kidney development are represented by Acantkias, Scyllium, and Rata. 



Inheritance of Coat-Colour in Rats.* — L. Doncaster gives the results 

 of experiments which dealt chiefly with the power of albinos to transmit 

 colour or pattern when mated with coloured individuals, and with the 

 nature and relations of certain of Crampe's types of colour. Albino 

 rats are not all similar in constitution ; some carry the determinant 

 for brown, others black, and others, again, both brown and black. So 

 also with pattern ; some carry the piebald character, some the " self " 

 (or " Irish "). There seems to be no doubt that the brown forms 

 (Crampe's types 1, 2, 3) correspond exactly with the similar black forms 

 7, 6, and 5, but are less simple to work with, since they may contain 

 recessive black. A point of some interest is the great diversity of 

 different litters from the same pair. Where enough offspring are reared 

 the results are in fair accord with Mendelian expectation, but in indi- 

 vidual litters this is often far from being true. Large numbers of 

 young, therefore, must be reared from each pair before the true pro- 

 portions are known with any accuracy. 



b. Histoloery. 



Intercellular Bridges and Leucocyte-Paths. f — Fr. Reinke discusses 

 the connection between intercellular bridges (and gaps) in epithelium 

 and the paths of migratory leucocytes. It may be that in cases like the 

 epithelium of an amphibian gill-plate, the epithelial cells were directly 

 in contact and formed a syncytium, and that the cells were first separated 

 by the immigration of leucocytes. Bridges and gaps were thus formed 

 as secondary results — as " paths of wandering cells." Increased lymph 

 pressure, associated with vigorous growth, would help. Indeed, three 

 factors must be recognised : (1) the wandering cells, (2) the pressure of 

 the lymph stream, and (?>) the contraction of the protoplasm. The 

 role of tropisms must be recognised : " epitheliophily " between epithelial 

 cells brings about a syncytium ; epitheliophily on the part of leucocytes 

 brings about immigration ; " leucocytophoby " on the part of the epi- 

 thelial cells induces "cytochorism"; and, finally, there is a " karyo- 

 phoby " between the leucocytes and the epithelial nuclei. 



Human Epiderm Cells. t — H. Schridde describes a remarkably 

 regular arrangement of the protoplasmic fibres connecting the different 

 cell layers of the human epidermis. These fibres, diagrammatically 

 represented, are in the form of an ellipse in the lower layers, and more 

 nearly circular towards the surface. At the points of crossing in the 

 deeper layers there is no thickening, but in the more closely situated 

 surface layers there is. Here, also, in the middle of the section of the 

 protoplasmic fibres in the intercellular spaces, occur knob-like enlarge- 

 ments, the " Ranvierschen Knotchen." Incidentally, it is noted that the 

 cerato-hyalin of the stratum granulosum frequently occurs in a clearly 



* Proc. Cambridge Phil. Soc, xiii. (1906) pp. 215-28. 



t Anat. Anzeig., xxviii. (1906) pp. 369-78 (3 figs.). 



X Arch. Micr. Auat., lxvii. (1905) pp. 291-301 (1 pi., 3 figs.). 



