1885. ] Embryology. 315 
weeks.” Mr. Caldwell states that he will leave a large number 
of the larve in an aquarium at the station in Queensland, and 
will also bring a supply of eggs to Sydney to rear in the labora- 
tory.— Nature. > 
EMBRYOLOGY.’ 
ON THE TRANSLOCATION FORWARDS OF THE RUDIMENTS OF THE 
Petvic Fins IN THE EmBryos OF Paysocuisr FisHEs.—The two 
great subdivisions into which the species of Teleost fishes are 
divisible, viz., the Physostomi and Physoclisti, stand to each other 
in the relation of the unspecialized and the specialized in respect 
to the evolution of the paired fins. The members of the group 
Physostomi tend to retain the pelvic limb more or less nearly in 
its primordial position throughout life, and no marked tendency 
towards the approximation of the rudiments of the anterior and 
the posterior limbs seems to be exhibited by the embryo, as may 
be seen upon studying the development of a form as typical of the 
group as the salmon or trout. Such retention of the primordial 
posterior position of the pelvic fins by the embryos of Physos- 
tomes supplements those other more unspecialized traits which 
they possess, viz., the open pneumatic duct, persistent throughout 
life, and the simpler or more primitive condition in later life of 
the paraglenal elements (coraco-scapular plate in the embryo), 
commonly differentiated in the adult into hyper-, meso- an po- 
coracoid, in Gill’s nomenclature, whereas in the Physoclisti the 
mesocoracoid is suppressed. The frequently persistent protop- 
terygian condition of a portion of median dorsal fin-system, de- 
veloped as a so-called adipose fin, is another embryonic character 
retained by many Physostomes. 
While the foregoing characters are unquestionably of value as 
determining the relative position of the two groups under discus- 
sion, I would now call attention to some embryological phe- 
nomena which demonstrate beyond any doubt that the Physo- 
clisti have descended from the Physostomi. 
In the young larva of Lophius, or the angler, taken from the 
egg shortly before hatching, A. Agassiz? has shown that the 
pectoral and pelvic fin-folds arise, the latter behind the former and 
almost synchronously, as lobate diverticula of the epiblast, into 
which mesoblast has been thrust outwards, and with their bases 
nearly horizontal. In this relation of position as anterior and 
posterior paired outgrowths they develop just as do the rudi- 
ments of the paired fins of the Physostomous salmon embryo; 
but the two pairs of fins are much more nearly synchronous in 
making their appearance, and are much closer together. The 
figure of the youngest stage of the angler given by Agassiz 
shows that there are but four myotomes opposite the interval be- 
1 Edited by Joun A. RYDER, Smithsonian Institution, Washington, D.C. 
2 On the Young Stages of Osseous Fishes, Part 111, 20 plates; Proc. Amer. Acad. 
Arts and Sciences, Vol. xvil, July, 1882 (Plates xvi, Figs. 2-5, and XVII, XVIII). 
