.  Leryza. 
METAMORPHOSES OF CRUSTACEA AND CIRRHIPEDS. 575 
as well as of the two large egg-capsules e, which are attached to 
it. Yet in its larval condition (fig. 313) it is an active little 
ereature, resembling in all essential particulars 
TF the larve of Entomostraca generally ; and from 
this type the males do not depart nearly so much 
as the females, the former retaining the general 
plan of structure, as well 'as the activity of habits, 
_ that prevail among the Entomostraca, whilst the 
latter lose their instruments of movement, acquir- 
; * ing the apparatus of suction and prehension. 
Fig. 313. 749. A still more remarkable example of meta- 
Lasv2 of mmorphosis is presented by the tribe of Cirrhipeds 
(§ 102), which, notwithstanding that they were 
long ranked as Mollusks, on account of their shelly invest- 
ment and their immovable attachment to solid bodies, are 
now known ito be so closely related to Crustacea, as in 
the opinion of many naturalists to rank merely as a sub- 
division of that group. The young, alike of the Lepas or 
“barnacle,” and of the Balanus or “ acorn-shell,” very much re- 
semble those of the ordinary Entomostraca ; they possess eyes 
and several pairs of motor appendages in this state ; and they 
swim freely through the water, after the manner of water-fleas. 
Before their last change, they are enclosed in a bivalve cara- 
pace like that of Cypris ; and they then possess a pair of 
large four-jointed” antennz, which are well furnished with 
muscles ; and it is by these antenne that the animal finally 
attaches itself, by means of a peculiar cement which is poured 
out from ducts running up into them from the body. In the 
- anterior of the recently-attached larva, the young Cirrhiped 
may be detected with its valves and cirrhi, like the embryo 
insect in its pupa-case ; and the carapace and integuments of 
the larva being thrown-off like a pupa-case, the perfect form 
is disclosed. In most of these animals, as in many mollusks, 
the sexes are united in the same individuals ; but when they 
are separate, the males are minute imperfectly-formed crea- 
tures, which lead a sort of parasitic life upon the surface of the 
females ; and in some of the hermaphrodite species “ supple- 
‘mental males” are also provided. 
750. Among the Rotifera or Wheel-Animalcules, the double 
_ mode of reproduction by agamic and by sexual eggs seems to 
be the ordinary rule. The former may go on at a prodigious 
