No. 403.] REVIEWS OF RECENT LITERATURE. 601 
the minute structure of the nephridia, made partly on fresh, partly 
on fixed material, form an important contribution to cytological 
knowledge. 
He finds that leucocytes (* excretophores ” ) play an active part in 
the process of excretion. Arising from the ccelomic epithelium, they 
become filled with excretory products in the lymph vessels, and then 
either migrate to the funnel apparatus of a nephridium, where they 
are broken up and give off their products to the canal cells of the 
nephridium, or else pass by amceboid movements through the walls 
of the lymph vessels and the muscle layers of the body to the epi- 
dermis, there to disintegrate. In either case they form the vehicle 
for the transportation, partial or complete, of excretory products to 
the surface of the body 
Pigment cells, the author finds, are a special variety of “ excreto- 
phore,” in which the excretory substance assumes a particular color 
as the cell passes to the epidermis. The formation of a definite 
color pattern in the leech is explained as the purely mechanical 
result of the migration of pigment cells along the path of least 
resistance toward the surface of the body. This leads to the 
aggregation of pigment in particular regions of the epidermis, 
especially between bundles of longitudinal muscles and in places 
where dorso-ventral muscles have their attachments. The foregoing 
explanation, perhaps, accounts adequately for such markings as 
simple longitudinal striations of a uniform color, but, in the opinion 
of the reviewer, fails to explain the more complicated color patterns 
of many leeches, in which corresponding regions of successive 
somites may be pigmented very ee or in colors strikingly 
contrasting. Ww f C 
The Resources of the Sea.— Professor W. C. McIntosh's vol- 
ume, Zhe Resources of the Sea as shown in the Scientific Experiments 
fo test the Effects of Trawling and of the Closure of Certain Areas 
off the Scottish Shores (London, C. J. Clay & Sons, 8vo, 248 pp., 
illustrated), sheds a deal of light on a very complex problem. It 
treats mainly of the Scottish fisheries, those of St. Andrews Bay, 
the Frith of Forth, Moray Frith, and the Frith of Clyde, but sum- 
marizes on British fisheries in general. The experiments tabulated 
cover a period of ten years or more; they relate to the effects of the 
use of trawls on the abundance of fishes, on the young, on the eggs, 
and on the food, and also to what may be effected in the way of 
replenishment by closure of particular areas. The value of the book 
