122 
SHIELD-SHRIMP. 
shanks ran piping and probing about the margin, 
and gulls and little terns screamed, cparrelled, and 
hovered over the heads both of bipeds and birds. 
As I stooped to collect some specimens of pond- 
snails in one of the clear freshwater ponds with a 
bottom of sandy mud, my attention was arrested by 
an object which at first sight I regarded as an 
unknown genus of bivalve mollusca, but on placing 
it in a bottle of water the real nature of the crea- 
ture became revealed. It was an Entomostracon. 
As a whale among minnoAvs, so, said I, is my new 
genus among AvateiHeas ; but again I was mistaken. 
I had not fished long before I brought to light a 
veritable apus, or shield-shrimp, and I saAv at once 
that my supposed new genus was the young of 
this ci^eature, thus illustrating very prettily the law 
in the development of organised beings, that the 
transition state of a higher form will represent the 
permanent condition of genera lower in the scale of 
being. I cannot find - any account nf the metamor- 
phoses of the Apodidee, or whether it is known that 
in the young state the shield is folded on itself 
