156 THE VOYAGE OF H.M.S. CHALLENGER. 



noirs en relief, interposle entre le vaisseau dorsal at le tube digestif." He notices the 

 different authors who have written about Cyamus, and the various names and systematic 

 positions which have been assigned to it. He himself considers that it comes nearest to the 

 Isopoda, though it ought not to be united with them. He objects to the term Lasmodipoda, 

 because the anterior feet are affixed to a special segment, not to the head or neck, as that 

 epithet would imply. After a definition of the genus Cyamtis, he defines his three species ; 

 L Cyamus ovalis, of which he says, "cette espfece vit agglomer^e sur les Eminences cornees 

 de la tete des Baleines franches (Balxna mysticetus)," herein, Liitken says, going astray ; 

 3. Cyamus erraticus, of which he says, " il vit errant, on le trouve sur la peau lisse, k la 

 base des tubercules corn^s, sur les nageoires, principalement aux aisselles et dans les plis 

 des parties gi^nitales et anales;" 3. Cyamus gracilis, of which he remarks, "il demeure avec 

 les Cyames ovales sur les protuberances de la tete." In a chapter on their " manners and 

 customs," he speaks of the prodigious quantity of the Cyamus ovalis and Cyamus gracilis 

 which can be seen a good way off at sea whitening the head of a whale, when it comes up 

 to breathe. He had reason to think that they must cause the whale no little irritation with 

 their sharp claws. Some care is needed in their capture, since these claws penetrate the 

 human finger like a needle, causing a sharp pain. Cutting the branchiaj did not seem to 

 affect these animals, but when their large antennae were cut, they would sway uneasily 

 about, as if they were drunk. He never found any in the stomach of the Albatrosses or 

 other sea-birds, which are sometimes supposed to help the whales to get rid of the parasites, 

 but he believed that the winter storms might be highly useful in this respect. He decisively 

 rejects the suggestion of MM. Audouin and Milne-Edwards that the Cyamus gracilis might 

 only be the young of the other species. 



1835. Gervais. 



Note sur deux espdces de Crevettes qui vivent aux environs de Paris. Annales 



des Sciences naturelles. Seconde Serie. Tome quatrieme. — Zoologie. Paris, 1835. 



pp. 127-128. 



The Crevettes d'eau-douce, he says, have been confounded under the names Gammarus pulex, 



aquaticus or jiuviatilis, as forming but a single species, whereas they really form two species, 



differing not only by zoological characters, but also by their habits. "Jamais elles ne 



s'accouplent ensemble, et I'une a sur le dessus des anneaux de I'abdomen des Opines que 



I'autre ne pr^sente pas." Eoesel and Geoffroy have described and figured the one, Desmarest 



and Zenker have figured the other. The former he proposes to call Gammarus Roeselii, 



because tlie names fluviatilis and aquaticus are inappropriate, since there is another river 



Gammarus, and all the Gammari are aquatic. His definitions are " Gammaeus pdlex, Fabr. 



Oculis reniformihus, antennis subsequalibus ; lingulo quoque ahdomis [cingulo quoque 



abdominis] leevi, id est non spinigero," and " Gammarus roeselii Nobis. Oculis aa antennis 



gammari pulicis, sed abdominis cingulo quoque aadeato, id est supernh et postice unispinigero. 



Astacus fluviatilis Eoesel. Insecten belistegungen III pi. 52. Crevette des ruisseaux Geofifroy. 



Hist, des Insectes pi. 21. fig. 6." I do not for my o\vn part consider Gervais justified by 



the reason he gives in altering Eosel's name. What he states as to the two species never 



mating is guarded in a note by the remark that such a thing might happen, without 



disproving the distinctness of the species. 



Gervais concludes as follows : — " On trouve aussi dans les environs de Paris, mais seulement dans 



I'eau de puits, une troisifeme sorte de Crevette, remarquable par la petitesse de sa taille, qui ne 



depasse pas en effet trois ou quatre millimetres. Cette Crevette, que nous consid&'ons 



comme une simple vari6te de sejour est constamment 6tiol6e, et ses yeux, au lieu d'etre 



