36 A HISTORY OF RECENT CRUSTACEA 
reverse. These organs are sometimes most dwindled in 
families which can claim a decided precedence over others 
in which these appendages are well developed. Thus they 
are short in the crabs, but long in the lobsters and shrimps, 
and short in the normal Isopods, but long or large as a rule 
in the Amphipoda, and within the Amphipoda they are 
short in the Orchestidz, a family that claims superiority 
by its tendency to terrestrial habits. 
Those who have made themselves acquainted with 
Professor Huxley’s volume, ‘The Crayfish, in the Inter- 
national Scientific Series, will be aware that in describing 
a crustacean appendage he names the first two joints the 
protopodite, which bears at its extremity on the inner side 
the endopodite, and on the outer side the ewopodite. For 
these terms the shortened forms exopod- and endopod will 
here be preferred—exopod for exopodite, endopod for 
endopodite and protopodite combined—and peduncle will 
be used for a variable number of basal joints. In the first 
antennee the peduncle consists, as already stated, of three 
joints, and by this circumstance the rule which widely 
prevails elsewhere that the so-called protopodite ends with 
the second joint of an appendage is broken without any 
obvious cause. Moreover, that which by its function and 
in general by its superior size appears to be the main 
branch is here the outer one, and not as usual the inner. 
It is conceivable that the exopod is wanting, that the main 
branch or principal flagellum is the true endopod, and that 
the secondary flagellum is an independent outgrowth. 
For the reasons mentioned, and some others, Dr. J. E. V. 
Boas considers that the first antennz are not homologous 
with the following limbs, but that both they and the 
stalked eyes ought to be regarded as limb-like sense 
organs. That besides being organs of touch, they are 
frequently organs of other senses, seems to be beyond 
doubt. In the Macrura at large the first joint contains 
an auditory apparatus. Sometimes the cavity is provided 
with a well-formed otolith or ear-stone. In the lobster 
and crayfish, Mr. Spence Bate says, ‘the perforation is 
long, narrow, and slit-like, the aperture being scarcely 
