23 
8UMMARI OF CURRENT RESEARCHES RELATING TO 
Las probably arisen from an optic centre, that of Vertebrates from an 
olfactory centre. 
Mollusca. 
a. Cephalopoda. 
Cliromatophores of Cuttlefishes.* * * § — Herr B. Solger maintains that 
the chromatopliore proper is a single cell which by its own metabolism 
forms pigment, and that the surrounding cells form an elastic capsule,, 
or that and radial muscular cells as well. He has shown by the methy- 
lene-blue method that nerves do really end in the radial cells, and is 
firmly convinced that these are muscular elements. 
y. Gastropoda. 
Anal Kidney of Larval Opisthobranchs.f — Dr. G. Mazzarelli, 
against Meisenheimer, Heymons, and others, vindicates his previously 
expressed conclusion that this organ (the “ anal-eye ” of Lacaze-Dutliiers 
and Pruvot) is of ectodermic origin, and persists in the free-living larvae 
of Aplysia, &c., after its closure. It does not disappear, as has been, 
stated, and is a definitive, not a primitive kidney. 
5. Lamellibranchiata. 
Pigment-formation in Lamellibranehs.f — Herr Victor Faussek has 
made an extended series of observations on the conditions necessary for 
the formation of pigment in the mantle, gills, and foot of Lamellibranchs, 
especially Mytilns. His results lead him to reject entirely Eyder’s view 
that light is the most important factor. Numerous observations with 
uninjured specimens, and with specimens deprived of the whole or part 
of the right valve, failed to show that light has any influence whatever; 
while the connection between the depth of pigmentation in any part of 
the body and the degree of oxygenation of the -water washing this 
region, is marked. The author succeeded in so adjusting specimens that 
the incoming current of water washed the anterior part of the mantle 
before reaching its posterior region, and found that this hitherto un- 
specialised and colourless region rapidly developed the peculiarities of 
colour and structure normally found only in the posterior region. The 
pigment is especially marked if the two regions of the mantle be sepa- 
rated by a deep cleft, a fact which, taken in conjunction with others,, 
leads the author to believe that the formation of pigment in Lamelli- 
branchs is due to the action of oxygen on a chromogen contained in the 
blood. Under normal conditions, therefore, pigment formation will occur 
only in organs freely exposed to the inhalant current, and the pigmen- 
tation will be most intense in that part of any organ which first receives 
the oxygenated water ; hence the tendency for pigment to accumulate in 
the posterior region of the mantle in most Lamellibranchs. 
Artificial Production of Pearls.§ — M. Louis Boutan describes a 
series of experiments made by him with a view to the artificial produc- 
tion of pearls. ChcosiDg Haliotis as the subject of his experiments,., 
* Arch. Mikr. Anat. liii. (1898) pp. 1-19 (1 pi.). 
t Biol. Centralbl. xviii. U898) pp. 767-74. 
X Zeitschr. f. wiss. Zool lxv. (1898) pp. 112-42 (3 figs.). 
§ Comptes Rendus, cxxvii. (1898) pp. 828-30. 
