+33) (file WILLIAM BATESON. 
Since the publication of these papers I have been able to 
make some further observations on the histology of the fresh 
tissues of the Brittany species (B. salmoneus and Robinii). 
For this opportunity I am indebted to the kindness of the 
directors of the Zoological Laboratory stationed at Concar- 
neau, Finistére. And especially my thanks are due to Dr. 
Chabry for affording me these facilities. 
The Skin and Nervous System. 
The skin of all the species is entirely ciliated. 
In the fresh condition I have chiefly studied it in B. 
Robinii, and it will be better first to describe its features in 
this form. Its structure is best seen by killing the tissue in a 
mixture of one part of 1 per cent. osmic acid and one of sea- 
water, then washing with sea-water, and staining with picrocar-. 
mine. This tissue on being teased out in glycerine shows the 
structure figured in figs. 76 and 77. The cells are very long, 
and most, if not all of them, extend the whole length of the 
skin (ef. fig. 75). The heads of these cells in the natural 
living state are closely in contact with each other, but on 
pressing out the tissue both in living and also in preserved 
specimens these heads may be stretched away from each other, 
but each remains attached to its neighbours’ by more or less 
regular anastomoses. It thus is brought about that the 
surface of the skin is made up of a sort of honeycomb of 
tissue, each of the nodes being the outer end of an ectoderm 
cell. The cells are very difficult to separate finely, but the 
skin may easily be broken up into small rectangular pieces. 
On separation each cell is very thin ; its outer end is slightly 
pyramidal, and is continued into a thin fibre which gives off 
anastomoses with adjacent cells and dilates at intervals. In 
one of these dilatations, generally the last, the nucleus is 
placed. Below this point the cell is continued into a very fine 
filament which may be traced for some distance. Many of 
these filaments terminate in small round knobs, which are 
possibly due to reagents. 
In sections of hardened specimens these filaments may be 
