86 QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE, 
These researches tend to connect the stem of the Insects with 
the Hedriophthalmatous Crustacea through the Myriapods. 
It appears that Packard’s recent observations on “ Develop- 
ment of Poduride” (‘Peabody Academy,’ vol. i) show that 
in these archaic insects there are no cell-structured em- 
bryonic membranes, but instead a chitinous skin, “like the 
larval skin of many Crustacea.’ Ulianin, of Moscow, has 
further found that Poduride agree with Myriapoda in having 
a total yelk-cleavage. 
Two points of grosser morphological (that is, relating to 
the plan of disposition of parts of a coarser or higher order 
than the ultimate cell-unit) significance may be cited here. 
Metschnikoff finds that the post-oral jaw-pieces are only two 
pairs in the Diplopods studied by him, viz. mandibles and 
the halves of the underlip, which fuse to form a plate, as 
do the second pair of maxille (third ‘ post-orals”) of In- 
sects. No trace of a second pair of maxille was found by 
Metschnikoff in Myriapods, nor by Packard in Poduride. 
On the other hand, it is not true that the Diplopod has a 
definite hexapod larval state. ‘The third, fourth, and fifth 
pairs of post-oral appendages are large, and develop early, 
but before the embryo escapes. Metschnikoff finds a sixth, 
seventh, eighth, and ninth pair of post-oral appendages, that 
is, seven pairs of legs in all, the hinder ones being, it is 
true, small (seven pairs in Julus, six pairs in Strongylosoma). 
Mollusca.—Salensky, in the Archiv fur Naturgeschicte, 
1874, has a paper on the Gastraea-theory, in which he offers 
some observations on the development of the common Oyster. 
He does not clearly apprehend the fact that there are two 
modes in which the diploblastic planula of Lankester (the gas- 
trula of Haeckel, and, as Salensky now calls it, the diblastula) 
develops in the animal series, namely, by invagination of a 
primitive hollow polyplast or multicellular sac, and by deda- 
mination from the inner wall of such a sac. Further, he is 
mistaken in supposing that the orifice of invagination observed 
by Lankester in various Mollusca has anything to do with 
the mouth. ‘Time will put this (which is a matter of fact) in 
its true light. 
Usoff has published a preliminary notice of observa- 
tions, carried out at Naples, on the development of the 
Dibranchiate Cephalopoda. His paper is deyoid of illustra- 
tions. One of his chief objects appears to be to demonstrate 
the existence of cell-layers corresponding not only to the 
epiblast and hypoblast of Vertebrates, but of tegumentary, 
vascular, and alimentary layers of the mesoblast. In his 
statements as to the origin of the eye, ear, and pen-sac being 
