ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
27 
foot and the mantle, and the author gives an account of the chief purposes 
to which these are put. He points out that, in trying to understand the 
habits and mode of life of this animal, he has but raised a few questions 
which he cannot answer, and that many more questions remain to be 
raised. He is quite right, we think, in considering that this line of re- 
search is one that deserves increasing attention, and though it may be 
admitted to be a difficult work, it certainly offers a key to the solution 
of many scientific questions of the present day. It is a return to the 
older methods of Natural History study, but with increased means at our 
disposal for appreciating the significance of our observations. 
y. Gastropoda. 
Hermaphroditism of Limpet.* — Mr. J. F. Gemmill reports some 
causes of hermaphroditism in the limpet, and makes some observations 
regarding the influence of nutrition in this mollusc. As is well known, 
the sexes are ordinarily separate, and the sexual apparatus is of the 
simplest kind. The author has lately found at Millport several limpets 
in which a gonad was not purely ovarian or testicular, but of a mixed 
character. Under the Microscoj>e there were at once seen not only ripe 
ova and spermatozoa, but also segmenting ova, and even ciliated free- 
swimming embryos. This hermaphroditism is of a kind much simpler 
than is usually found in hermaphrodite species of the same order, and 
rather approaches the type seen in the common oyster. The peculiar 
habits and structure of the limpet may give a key to this occasional 
variation. As the limpet is solitary and practically fixed, and as it has 
no organs of copulation, and as no sexual congress of any kind has been 
observed, the meeting of ova and spermatozoa would seem to depend 
on chance, so that occasional hermaphrodites might be of benefit to the 
species. The number of such variations, however, is too small to allow 
this consideration much weight. Apparently they have till now escaped 
observation altogether, and out of about 250 specimens the author found 
only three hermaphrodites. With regard to the stations they occupy, 
limpets may be divided into high-level, middle-level, and low-level 
forms, and it is clear that the amount of nutrition which these three 
kinds would get would differ considerably. One might expect that if 
nutrition has any influence on sex, such an influence would make itself 
seen in the different proportions of male and female specimens at different 
tidal levels. In accordance with current theories it may be thought 
that the low-level limpets, with their richer nutrition, would show a 
relatively greater proportion of females over males. Figures, however, 
show that this is not so ; and the conclusion must be come to that — in 
the limpet, at any rate — more abundant nutrition does not predispose to 
the female type. It must, however, be borne in mind that the female 
gonad of the limpet is not larger in bulk than the male, and does not, 
therefore, make special demands on nutrition. 
8. Lamellibranchiata. 
Green Oysters again.f — Sig. D. Carazzi has made an elaborate 
study of the green oysters of Marennes. His chief conclusions are the 
* Anat. Anzeig., xii. (1896) pp. 393-4. 
f MT. Zool. Stat. Neapel, xii. (1896) pp. 381-431 (l pi.). 
