The Crab Parasite, Sacculina

S OME three years ago I received a small number of crabs, pre- served in alcohol, that had been collected by Dr. Van Elsen in the neighborhood of Tampa, Hillsboro county, Fla.The scientific name of the crab is Panoptets herbstii, described by A. Milne-Edwards, a crustacean which has been introduced from farther south, Key West, the West Indies and Brazil, where it occurs most abundantly.Once in a great while an occasional straggler from those southern waters is found on the shores of New Jersey, Long Island and Connecticut.Three other species of the genus Panopawus permanently occur from Florida up to the New England States, Panopcus larrisii, P. depressus and P. sayi.Our P. kerbstii is easily distinguished from the other three species, as taught by Professor S. I. Smith, of Yale College, " by a tubercle on the sub-hepatic region, just below the first lobe of the antero-lateral border of the carapax, also by the post-orbital tooth being separated from the second tooth of the antero-lateral margin by a rounded sinus, and by the dactylus of the larger cheliped having a stout tooth near the base within."It is well known that all these Panopweus species largely contribute to the food of many marine fishes.So much for the Panopaeus.But our P. /ze-bstii does not so much interest us at present as does its enemy, which is also a crustacean, living parasitically on its host.It does, however, not parasitize in the gill-cavity of its host, as is the case with the parasite Bopyrus infecting the common shrimp of our shores,