Elysia timida (Risso, 1818) three decades of research

During the last 30 years, studies on Elysia timida (Risso, 1818) have addressed various aspects related to food sources, photosynthetic efficiency of kleptoplasts, population genetics, chemical ecology and reproductive biology, both in the Mediterranean Sea and in the Mar Menor coastal lagoon. E. timida shows a strong specific interaction with Acetabularia acetabulum, retaining functional chloroplasts for at least 45 days and obtaining extra energy in periods when food resources are scarce. It shows control of parapodia, avoiding pigment photodestruction under oversaturated light conditions. The chemical ecological relationships established between E. timida and its potential predator fish, Thalassoma pavo, have also been evaluated, and it has been found that that the extracts of the mollusc contain repellent and unpalatable polypropionate compounds. Population genetics has demonstrated the genetic divergence between populations showing high and significant values of FST and genetic distances, and at least six privative alleles that are not shared with Mediterranean populations have been detected in lagoon populations. This sacoglossan is a poecilogonic species, and its lagoon populations show a greater reproductive output than Mediterranean populations; they produce a greater number of egg masses and embyros per individual, and the capsules have a wider diameter.

Letter from William Croswell to Daniel P. Colesworthy, 1818 January 8

Draft of a one-page letter concerning the payment of a bill and mentioning Croswell's health.

Letter from Sarah Bumstead to William Croswell, 1818 January 15

One-page letter from Croswell's sister with news about her activities.

Letter from William Croswell regarding Mrs. Collins, 1818 February 19

Draft of a one-page letter to an unidentified recipient regarding payment to Mrs. Collins for washing.

Letter from William Croswell to Ephraim Eliot, 1818 November 10

Draft of a one-page letter thanking Eliot for money.

Note from William Croswell to Levi Frisbie, 1818 November 30

Brief note with a complaint about the servant of Levi Frisbie, Harvard Professor of Natural History.

Letter from William Croswell to John Davis, 1818 December 5

Draft of a one-page letter to Judge John Davis regarding a mathematical problem.

Harvard College quarter bills, 1812-1818

This folder contains sixteen printed Harvard College quarter bills filled out in manuscript primarily for William Croswell's use of wood.