helmet of the water flea (Daphnia spp.) does not make it invisible, but it does confer some protection against predators by making the fleas harder to catch. Water fleas do not necessarily begin life with a helmet but can form one as a morphological defence in response to chemicals released by their predators. The images above show three pairs of water fleas from different species; the non-helm...

Although the enzymatic synthesis of S-adenosylmethionine was accomplished several years ago (l), there have, as yet, been few reports of experiments with this compound. The main reason for the paucity of data appears to be the difficulty of obtaining S-adenosylmethionine in adequate quantities at a reasonable expenditure of time and starting material. Cantoni (2) has prepared S-adenosylmethioni...