Abstract
HALF of this interesting study is taken up by a paper on “Seeing without Eyes,” in which the author considers the general question of sensitiveness to light, with illustrations from his own researches. In the second half these researches are described, and some special questions more fully discussed. The author's own observations were made chiefly on lamellibranchs and gasteropods, and showed a high degree of sensitiveness to light in the absence of anything like a visual organ. He found that some molluscs reacted especially to diminution, others to increase of light, and that this difference was correlated with other characters; those molluscs with soft shells, which bury themselves in the sand, reacted strongly to light, while those with hard shells responded more to shade. He found the highest degree of sensitiveness to light in Psammodia; and it is interesting to note, in relation to the common view as to the connection between sensitiveness to light and pigment, that the impregnated siphons of this mollusc were highly sensitive. Another interesting point investigated was the influence of repetition of a light stimulus. An oyster or mussel which has reacted to a shadow will react much less strongly, or not at all, to a second stimulus, even if much more intense, and does not recover its previous degree of excitability till more than an hour has elapsed. The book concludes with a full bibliography.
Der Lichtsinn angenloser Tiere.
By Dr. Wilibald A. Nagel. Pp. 120. (Jena: G. Fischer, 1896.)
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Der Lichtsinn angenloser Tiere. Nature 54, 341 (1896). https://doi.org/10.1038/054341c0
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DOI: https://doi.org/10.1038/054341c0