492 PROF. OWEN ON THE ANATOMY 
Nauplii and Amymone are entered among the synonyms of the full-grown parents to 
which they severally belong—as, e.g., to Canthocamptus minutus, Baird, C. stromii, C. fur- 
catus, C. chelifer, &c. The * Nauplius’ of Balanus, i. e. the young of that Barnacle after 
quitting the egg, is a free * hexapod,’ with relatively larger swimming-limbs, furnished 
with more numerous and relatively longer setze than in N. saltatorius *. 
Fig. 9. 
Nauplius saltatorius (young of Cyclops). 
(After Baird, op. cit. tab. xxiv. fig. 9.) 
sie enn (young of Apus) eur dmm 
fter Baird, op. cit. tab. i 2.) 
Thus it appears that Nauplius is not a ‘thing’ but a ‘name.’ That is, the term 
means not one but many things, and all of them known more truly or scientifically under 
other * nomina” of multitude, both generic and specific. 
It is essential in this part of my memoir to hold an intelligible idea of what is signified 
by Nauplius, in reference to its application to the question whether the embryonal de- 
velopment of Limulus is a ** recapitulation of the history of all its ancestors," or merely 
a manifestation of the phases of its own specific growth—and if the latter, whether any 
of those phases resemble not a Nauplius only, but other species or genera of Crustacea, 
more, and in more essential characters, than they resemble later phases or the generic 
characters of the parent. 
At the phase of development of Limulus (fig. 4) which is called the * Nauplius stage’ +, 
the resemblance is as follows: the limbs are restricted to the part of an undivided 
body answering to the later-defined cephaletral division, as yet not distinctly marked 
out. The correspondence of the embryo Limulus to the young Entomostracan is 
carried no further. The cephaletral limbs in the former are mere buds; the terminal 
joint is bent on the proximal one; there is no trace of setze, not the slightest indication 
of any transitional natatory structure or function of such embryonal limbs. The mouth 
opens, almost, in its limuline relations to the antennules (11) and antennæ (111); and 
these already show their characteristic difference of size. Their next step is to gain the 
prehensile chelate structure, as in the adult. What the “famous Nauplius” may be 
I have not been able to make out; but if the stage in question really represents any 
“ common ancestor," it certainly is not the Nauplius of carcinologists. It may also be 
remembered that Zimulus differs from the parents of Nauplii, i. e. Copepods, Phyllopods, 
and other Nauplian Entomostraca, in the eggs being left to hatch in a sand nest, not 
carried about in egg-bags. 
* C. Spence Bate, “On the Development of the Cirripedia," in ‘Annals and Magazine of Natural History, 2nd 
Series, vol. viii. (1851) p. 324, pl. vi. fig. 1, Balanus balanoides ; fig. 5, Balanus perforatus. 
+ Packard, loc. cit. pp. 163, 202. 
