512 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
closing the blastopore, and results in tbe formation of a ventral meso- 
dermic layer, which occupies the whole ventral surface and surrounds 
the gut on both sides. This unified mesoderm is lost in the course of 
development, and in the trochophore stage the elements are irregularly 
scattered in the segmentation cavity, without forming any secondary 
coelom. Herr Tonniges follows the differentiation of the mesoderm 
to the origin of the pericardium, and takes a general survey of what 
has been previously observed as to the formation of the mesoderm in 
Gastropods. 
Experiments on Molinscan Eggs.* — Mr. J. Fujita undertook some 
experiments on molluscan eggs, with the hope of determining the exact 
fate of an isolated blastomere. A species of Aplysia, common at the 
Misaki Marine Laboratory, laid eggs well suited for the purposes of 
this research, which, however, the author was unable to complete. The 
general conclusion at which he arrives is that isolated blastomeres have 
in every case energy to restore the lost portion, and to reassume the 
normal shape. Unfortunately, printers’ readers in Japan are not, or 
appear to be not, sufficiently well acquainted with English, and the 
result is that there are so many misprints in the article that one often 
feels difficulty in being certain as to what the author exactly means. 
5. Lamellibrancliiata. 
Staining in the Oyster.t — M. J. Chatin gives an account of the 
staining of the oyster, due to disease. These diseased and stained 
oysters have a very different appearance to the ordinary green or brown 
oysters ; the coloration is not intense and localised, but pale and 
diffused; the retraction of the gills and the softness of the flesh are 
sufficient to show that the creatures are diseased. The origin of this 
affection is to be found in the organ which is often called the liver. The 
general characters of this organ become modified; the pigment-cells 
predominate, their protoplasm becomes altered, and, while some remain 
intact, others float in a thick liquid. While these modifications are to 
be seen in the secreting elements, others happen to the connective tissue. 
Here there is considerable increase in the size and number of the glan- 
dular cells ; budding and growth are succeeded by degeneration. When 
this happens, phagocytosis, which is so frequent and so active in the 
oyster, becomes apparent. When migrating cells absorb the free pig- 
mented granules or attack the glandular cells and carry off their pigment, 
the phagocytes, getting into the blood, disseminate the colouring matter, 
which soon impregnates the whole of the mantle. The author directs 
particular attention to the difference between these phenomena and that 
to be seen in the healthy coloured oyster. 
Macroblasts of Oysters.^ — M. J. Chatin has studied the origin and 
localisation of the macroblasts of oysters, and finds that they are derived 
from connective tissue. The frequency of the presence of these elements 
at the tip of the branchial papillae is due to the feebleness of the resist- 
ance of the epithelium in that region. 
* Zool. Mag., viii. (1896) pp. 47-54 (1 pi.). 
f Comptes Kendus, exxii. (1896) pp. 1556-9. X Tom. cit., pp. 796-9. 
