Experiments and Observations made at the Plymouth 
Laboratory. 
By 
J. T. Cunningham, M.A. 
PAGE 
I. Diagnostic Characters in Flat Fishes. < . - 247 
II. The Development of the Egg in Flat Fishes and Pipe-fishes - - 208 
III. A Piebald Plaice . : : ° ° ° a aril 
IV. Growth and Distribution of Young Food-fishes . : E 5 Ue 
V. Notes on Rare or Interesting Specimens c 5 ; - 274 
I. Diagnostic CHaRActEeRS IN Fuat Fisaes. 
One of the objects of zoological study is to ascertain more com- 
pletely and more accurately the peculiarities by which one kind of 
animal (species, variety, genus, Wc.) is distinguished from another. 
The advance of our knowledge in this direction depends on the 
more minute examination and more accurate distinction of known 
forms, the examination of larger numbers of specimens from familiar 
localities, and the examination of specimens from localities pre- 
viously unsearched. There is scarcely any family so thoroughly 
investigated that it does not yield new discoveries on a renewed 
examination of more abundant material. It is found possible to 
recognise finer distinctions, and so split up one species into several, 
or convert what was considered a species into a genus. New mate- 
rial—that is to say, examination of a large number of specimens— 
often shows, too, that distinct species are more or less connected by 
intermediate forms. But in all this work the part played by these 
minute peculiarities in the hfe of the animal usually receives little 
attention. It is not the object of systematic zoology to ascertain 
the uses of characters, or to explain their origin. These objects 
require different methods, and are usually pursued by different 
NEW SERIES.—VOL. III, NO. lV. Pa! 
