- CHAPTER I. 
STRUCTURE OF THE MEDUSZ. 
To give a full account of the morphology, develop- 
ment, and classification of the Medusze would be 
both unnecessary for our present purposes and 
impracticable within the space which is allotted to 
the present work.* But, for the sake of clearness 
in what follows, I shall begin by briefly describing 
such features in the anatomy of the jelly-fish as 
will afterwards be found especially to concern us. 
In size, the different species of Medusz vary 
from that of a small pea to that of a large umbrella 
having streamers a hundred feet long. The 
general form of these animals varies in 
different species from that of a thimble 
(Fig. 1) to that of a bowl, a parasol, or 
a saucer (see figures in subsequent chap- 
ters). Or we may say that the form of 
Fi . l— . 
Sarsia the animals always resembles that of 
(natural 
size). a mushroom, and that the resemblance 
* Those who may desire to read an excellent epitome of our 
most recent knowledge on these subjects, may refer to Professor 
E. Ray Lankester’s article in the “ Encyclopedia Britannica ” on 
“ Hydrozoa,” together with Professor Haeckel’s Report on the 
Medusz of the Challenger Expedition. 
