Sept. 1, 1870.] 



HARDWICKE'S SCIENCE-GOSSIP. 



199 



aberrant Isopod of the family Idotaa, the Slenosoma 

 of Leach, and the Idotee lineaire of Milne-Edwards, 

 and he looks like the marine equivalent of our ter- 

 restrial myriapods, although he is only furnished 

 •with seven pairs of legs, which are adapted rather 

 for walking than swimming. 



"L'abdomen ne porte point d'appendices a, son 

 extremite, mais est garni en dessous d'un appareil 

 operculaire tres-developpe, destine a clore une 

 cavite respiratoire ou se logent les fausses pates 

 branchiales." It is interesting to watch the rapid 

 fluttering of these opercular valves, and to observe 



the fish in the nets." They are much used by the 

 Mediterranean fishermen for bait, who catch them 

 by sinking bundles of Fucus ericoides, which, on 

 being hauled up, are found covered with Isopods 

 and Talitri. 



We have caught one of those odd things, the 

 Pycnogons, commonly called "£ea Spiders," from 

 their apparent outward resemblance to the 

 Arachnida. Dr. Anton Dohrn, who has recently 

 written on their embryology, is of opinion that they 

 are true Crustaceans. Although they are common 

 enough everywhere, they seem to be still a puzzle 



Fig. 185. Nymphon gracile, x 10. C. Barron, Ad. Nat. Delt. 



how their action insures the ceaseless flow of an 

 ever-changing and ever-renewed current of water 

 over the branchial plates. A Monsieur Roux, who 

 has written about the habits of the Idotcea, says': 

 "They abound where the sea has brought together 

 masses of algse in a state of decomposition ; here, at 

 a depth of a foot or two in tranquil water, they 

 multiply rapidly, feeding voraciously on dead fishes, 

 mollusks, annelids, and other animal matters, 

 gnawing also the meshes of the nets of the fisher- 

 men. They are essentially nocturnal, hiding under 

 marine plants by day, coming forth after dark to 

 feed ; sometimes in such vast numbers as to damage 



to naturalists. It is said that they live parasitically 

 upon Cetacea, and even upon some of the Medusae ; 

 but, as far as we can judge, nothing, or next to 

 nothing that is absolutely reliable, is known about 

 them. We find them in abundance under the stones 

 and roots of weeds at low watermark, which we 

 fancy is their natural habitat, where they probably 

 feed and live much after the manner of other small 

 beach-haunting crustaceans. When disturbed or 

 carried away by the tide or the waves, they, like 

 other creatures, will catch hold of anything, from 

 whales to sea-blubbers, that may come in their way. 

 We can only present our readers with a faithful 



