The voyage of the Beagle
June 3rd.?Yerba Buena to Carizal. During the first part of the day we crossed a
mountainous rocky desert, and afterwards a long deep sandy plain, strewed with
broken sea- shells. There was very little water, and that little saline:
the whole country, from the coast to the Cordillera, is an uninhabited desert.
I saw traces only of one living animal in abundance, namely, the shells of a Bulimus,
which were collected together in extraordinary numbers on the driest spots.
In the spring one humble little plant sends out a few leaves, and on these the
snails feed. As they are seen only very early in the morning, when the ground is
slightly damp with dew, the Guascos believe that they are bred from it.
I have observed in other places that extremely dry and sterile districts,
where the soil is calcareous, are extraordinarily favourable to land-shells.
The Descent of man-Chapter 9 The Gasteropoda, though capable of locomotion and furnished with imperfect eyes, do not appear to be endowed with sufficient mental powers for the members of the same sex to struggle together in rivalry, and thus to acquire secondary sexual characters. Nevertheless with the pulmoniferous gasteropods, or land-snails, the pairing is preceded by courtship; for these animals, though hermaphrodites, are compelled by their structure to pair together. Agassiz remarks, "Quiconque a eu l'occasion d'observer les amours des limacons, ne saurait mettre en doute la seduction deployee dans les mouvements et les allures qui preparent et accomplissent le double embrassement de ces hermaphrodites."* These animals appear also susceptible of some degree of permanent attachment: an accurate observer, Mr. Lonsdale, informs me that he placed a pair of land-snails (Helix pomatia), one of which was weakly, into a small and ill-provided garden. After a short time the strong and healthy individual disappeared, and was traced by its track of slime over a wall into an adjoining well-stocked garden. Mr. Lonsdale concluded that it had deserted its sickly mate; but after an absence of twenty-four hours it returned, and apparently communicated the result of its successful exploration, for both then started along the same track and disappeared over the wall.
* De l'Espece et de la Class. &c., 1869, p. 106. Home