ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
407 
albumen which is sucked out by the larva from the mother, whose 
dimensions now begin to shrink very markedly. From this second 
stage the adult is gradually developed. 
Segmentation appears at first either total or partial, according as 
the deutoplasmic portion is more or less involved, but the partial mode 
predominates, and the result is a core of yolk with peripheral cells, — 
some large, which form the blastoderm, others very small, which become 
applied to the vitelline membrane. The blastoderm shows an invagi- 
nation, followed by a deep groove, which is bounded by five paired 
groups of ectodermic cells — the first hints of appendages. Mesodermic 
elements arise as groups of cells from the wall of the invagination. 
The nutritive vitellus, which showed no trace of cellular elements after 
the formation of the blastomeres, begins to show endodermic nuclei. 
This first embryonic stage is covered by a cuticular layer especially 
thick at the level of the invagination and groove. 
From the invagination and groove is formed the suctorial apparatus, 
aud groups of mesoderm cells form muscles. The endodermic nuclei 
of the vitellus form a transitory digestive sac. 
This sac is replaced in the larva by the suctorial apparatus which 
takes up the whole body. Its structure is described. 
The suction results in the accumulation of much albumen in the 
general cavity of the larva — a second vitellus, in short. This deut- 
embryo stage is marked by swelling, moulting, thickening of the 
appendages, the appearance of- the first appendage, and the nervous 
system. 
The suctorial apparatus is excluded from the body of the embryo 
and forms an appendage lodged for a long time in the cavity which 
leads to the stomodseum and attached to the rest of the body by the 
“umbilical cord.” Barrois completes his account, of which we have 
only given excerpts, with a description of the development of the 
nervous system and mesoderm segments. 
Spiders of Central Australia.* — Mr. H. K. Hogg reports that, while 
as yet very few specimens of spiders from the desert and sandy country 
of Central Australia have been seen by zoologists, the Horn expedition 
brought down 150 specimens, well distributed over the various tribes 
and orders, and comprising 57 species, while nearly one-third of these 
are as yet undescribed ; they present a general analogy to those of the 
coast districts of New South Wales and Queensland, exhibiting here and 
there interesting variations in what are clearly co-ordinate types. The 
differences in shape and measurement are such as might be expected to 
be developed during an isolation extending over a comparatively long 
period. They consist chiefly of such points as longer or shorter legs, 
relative distances and sizes of eyes, bespining, absence of patterns, and 
shapes of genital organs, rather than differences in colouring, which 
might naturally be looked for among differently coloured soils. 
Secondary Spiracles of Opilionidse.f — Herr J. C. C. Loman directs 
attention to H. J. Hansen’s discovery of spiracles on the legs of 
Opilionidae, fam. Phalangiidse. The tracheal system of Opilionids 
* Horn Scientific Expedition, pt. ii. (1896) pp. 309-56 (1 pi.), 
f Zool. Anzeig, xix. (1896) pp. 221-2. 
2 f 2 
