OF THE AMERICAN KING-CRAB. 491 
Limulus, afforded by specimens preserved in alcohol, transmitted to him by Dr. Packard. 
They are confirmatory of the accuracy of the observations of the able American em- 
bryologist as detailed and illustrated in the work above cited. Dr. Dohrn premises 
a German translation of Dr. Lockwood's memoir in the * American Naturalist, and of 
the Abstract (which appeared in the same periodical) of Dr. Packard's Memoir. The 
chief characteristic of the contribution by the German carcinologist lies in the point 
of view which he has taken of the phenomena. It is a development of that sketched 
out as follows, in my ‘ Lectures on Crustacea’ of 1843 and 1858. “ To what end, 
it may be asked, tends all this discussion concerning the affinities of animals that 
have long ceased to exist? How are we concerned with it in considerations relative to 
the generation and development of the actual Crustacea ? To this I have to answer, that 
it is only by a knowledge of the transitional larval forms of these that we come rightly 
to comprehend the nature and affinities of the extinct Trilobites, and that our knowledge 
of the most interesting relations of actual larve requires a previous knowledge of the 
Jorms of their class that have heretofore existed on this planet" *. This view is developed 
and illustrated as follows by Dr. Dohrn :—* Fritz Müller himself made the first decided 
application of this ‘law,’ viz. that the embryological development was nothing more or 
less than a short, though not always exact, recapitulation of the history of all the 
ancestors of the organism in question—by tracing the different orders of the Crustacea 
back to their common ancestor, the famous Vauplius, that little crustacean larva that 
quits the egg and is afterwards gradually developed into the well-known diversified and 
more highly organized forms ” 
It may not be out of place q to recall what is understood in plain matter of fact by 
the term Nauplius, as contrasted with its transcendental signification. 
The young of Entomostraca, with ciliate natatory limbs (cuts, figs. 9 & 10) more or less 
like those of the parent, want, when hatched, the protective bivalve-like cephaletral 
shield and some other parts of the adult, yet soon show characters which enable the 
student of the group to refer them to their species, the full diagnosis of which they yield, 
as in Limulus, after successive ecdyses. 
The first systematic observer of the small representatives of the subclass 1, not knowing 
the genetie relations of his subjects, referred the young of some species to distinct genera 
—those of Cyclops ( Canthocamptus) minutus e. g. to G. Amymone, and the hexapod stage 
of Cyclops quadricornis to Nauplius. Later observations have led to their being rele- 
gated to their proper species $. Nauplius saltatorius, O. F. M. (fig. 10), is the young of 
Cyclops quadricornis; Nauplius bipes (fig. 9) is the larva of Apus cancriformis: other 
poden, I. Cumaceen, 8vo; ‘II. Pyenogoniden;’ ‘III. Daphnie, Svo, 1869; ‘ Die Schalendriise u. pum 
Entwicklg. d. Daphnien,’ 8vo, 1869; * Ueberreste d. Zoéastadiums in d. ontogenet. Entwickel. d. verschied. Crustac.- 
Fam.’ 8vo, 1870; * Unters. üb. Bau u. Entwick. d. Arthropoden, I, & II., 8vo, 1870. 
* * Lectures on Invertebrata,’ 8vo, ed. 1855, p. 333. 
T Dr. A. Dohrn, in the * Academy” for Nov. 1, 1871, p. 429. 
+ * Entomostraca, seu insecta testacea, que in aquis Danie et Norwegiæ reperit, descripsit et iconibus illustravit, 
Otho Fred. Müller, 1785. 
$ See the excellent work ‘The Natural History of the British Entomostraca, Svo, 1850, by W. Baird, 
M.D., F.LS. 
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