628 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
antennm in Pinnotheres and Leucosiidge, the variable development of the 
lateral laminae of the telson, the disappearance and subsequent re- 
appearance of some appendages (first maxillipede in Scyllarus ). 
As phylogenetic characters of the zoea may be noted the presence 
of the unpaired nauplius eye, the persistence of the exopodite in two or 
more thoracic appendages, the presence of the ganglionic chain in the 
abdomen of Brachyura, the distinctly bilobed mandibles in Brachyura, 
the presence of the mobile spine on the second antennae, and the charac- 
teristic form of the anal segment. 
The systematic relations of the Oxyrhynchi may be thus expressed : — 
Maiadae 
Partlienopidae 
Inachidas 
Latreillia 
Development of Maia Squinado.* — Herr F. Urbanowitz gives a 
preliminary account of the development of this Crab. From the ventral 
blastoderm small cells migrate into the vitellus, forming a transitory 
endoderm; a few which remain near the blastoderm form the first 
rudiment of midgut. Almost all the mesoderm of the nauplius is like- 
wise transitory, and its degeneration is briefly described. In connection 
with the origin of the nervous system the author notes the appearance 
of a pair of ganglia, to which no appendages correspond, and which may 
be regarded as homologous with the “ primary brain ” of Copepods. 
Embryology and Histogeny of the Isopoda.t — Herr Jozef Nusbaum 
has investigated this subject chiefly on Ligia oceanica and Oniscus 
murarius. 
With regard to the origin of the germ-layers in Ligia , the endoderm 
arises from an unpaired posterior median solid rudiment, the mesoderm 
chiefly from two paired lateral regions of the primitive three-cornered 
embryonic disc. The mesoderm then forms rows of cells arranged very 
regularly. The posterior and most important of the cell-rows are formed 
from the paired lateral regions, but the central rows seem to be largely 
formed from the endoderm. The ectoderm shows a somewhat similar 
arrangement in rows. The liver outgrowths and the rudimentary 
mesenteron are formed in a very complicated manner by the endoderm 
rudiment, which flattens out, becomes paired, and surrounds the yolk. 
The body-cavity is formed by the fusion of spaces arising between the 
mesoderm cells. 
* Biol. Centralbl., xiii. (1893) pp. 348-54. 
+ Abh. Krakauer Akad., xxv. (1893) (6 pis.) (Polish); Biol. Centralbl., xiii. 
(1893) pp. 429-35. 
