Larrdl Sfa(j(:s of 2'rilobifrs. — Hct'cher. 187 
recalls this tyi)e, but, as alread}- suggested, is removed some 
distance from the prototjq^e, although in itself n most primi- 
tive cfustaeean. Lang-"' gives a very comprehensive de- 
scription of the racial form, as follows: "The original Crustace- 
an was an elongated animal, consisting of numerous' and 
tolerably homonomous segnu-nts. The heatl segnu^nt was fused 
with the 4 subsequent trunk segments to form a cephalic re- 
gion, and carried a median frontal eye, a ]>air of sim])le ante- 
rior antennje, a sc^cond pair of biramose anteniue and ',\ pairs 
of biramose oral limbs, which already served to some extent for 
taking food. From the ])osterior cephalic region proceeded an 
integumental fold which, as dorsal shield, covered a larger 
or smaller portion of the trunk. Tlie trunk segments were 
each provided with one pair of biramose limbs. Besides the 
median eye there were '1 frontal sensory organs. Tlie nervous 
system consisted of brain, (esophagacl commissures and seg- 
mental ventral clu)rd, with a double ganglion for each segment 
and pair of limbs. The heart was a long contractile dorsal 
vessel with numerous pairs of ostia segmentally arranged. In 
the racial form the sexes were separate, the male with a pair 
of testes, the female with a i)air of ovaries, l)oth with ])air(Hl 
dvicts emerging externally at the bases of a pair of trunk lind)S. 
The excretory function was carried on by at least 2 pairs of 
glands, the anterior pair (anteiinal ghinds) emerging at the 
base of the second pair of antennte, the posterior (shell glands) 
at the base of the second ])air of maxilhe. The mid-gut ]K)ssi- 
bly had segmentally arranged diverticuhi (hepatic invagina- 
tions)." 
The characters ascril)ed to the typical nauplius have been 
selected mainly on the ])rinciple of general average. They do 
not satisfy the theoretical demands resulting from a compara- 
tive morphological study nor are they consistent with the ac- 
cepted requirements of an ancestral type of tlie Crustacea. 
Clausi*' virges tliat the naui)lius is a modified or secondary lar- 
val form, and the writer now hopes to farther substantiate this 
view, and part ly to reconstruct the nauplius d'om internal evi- 
dence and from its more ])rimitiv<- representative, the protas- 
pis of the trilobites. 
The usual fetaures attributed to tile nauplius are: three 
pairs of ai)]»en(higes. afterwards forming two ])airs of anteniue 
