236 EEPOKT— 1880. 



separates the general cavity of the respiratory chamber, produced by a 

 special mechanism. 



M. Jobert found this respiratory chamber largest in Uca Una, the 

 reflexion of the membrane most developed, the vascular vessels the most 

 numerous. Gelassimus, he says, may be considered as possessing an 

 organism nearly as perfect. Among the Grapsi, which live half of their 

 time under water, the respiratory cavity is diminished by the flattenino- 

 of the carapace, and the vascular network is less abundant. 



Under all circumstances M. Jobert found a respiratory organisation 

 similar to that which exists in all Crustacea, but capable of undergoing a 

 distinct usage. The organisation consists of a simple cavity, the membrane 

 which lines it is furnished with vessels ; one carrying deoxygenised 

 blood, the other returning it to the heart without passing it through the 

 branchiffi, after it has been brought into contact with air that has been 

 incessantly renewed. Moi-eovei-, this membrane is covered by a pellicle 

 which precludes desiccation and fulfils the part of a veritable epidermis. 



In consequence of the observations which M. Jobert has made, he 

 proposes to call the Crustacea so organised by the name of ' Branchio- 

 pulmones,' in consequence of the capability by which their structure per- 

 mits them to adapt themselves to atmospheric respiration, while they 

 possess an anatomical arrangement that is essentially aquatic. 



Professor Huxley has recently given much attention to the arrange- 

 ment of the branchia in Crustacea, and has done good sei-vice in suggest- 

 ing a tabulation of them under a distinct nomenclature. 



The position of the bi-anchial plumes are constant throughout the 

 several orders, and are absent or present according to specific or generic 

 variation. He thus has proposed that each plume should be distinguished 

 by a name that will at once recognise its position, and has proposed the 

 following classification. The branchia that is rooted to the coxa of the 

 several pairs of pereiopoda he calls imdohmnchia. The two that are 

 situated on the articulating tissue that unites the appendnge Avith the 

 body of the animal, he calls anterior or posterior artliropoda, and the one 

 that originates from the side or wall of the .several somites of the pereion 

 lie calls pJeurohmnchia. To the long flabelliform lash that is so liable 

 to vary both in form, size and number, he uses the two names proposed by 

 Milne-Edwards for the same homotypical part, when attached to the organs 

 of the mouth, or when ap]3ended to the leet, namely, the Ejngnathe and 

 epipodite, an inconvenience that he himself lias expressed when writing of 

 the same in his work on the Crayfish. This, Milne-Edwards in his 

 earlier works recognised by the title of the flabelliform appendage. It 

 appears to me therefore that a term recognising the part in its true 

 relation wherever existing will be found both more convenient as well as 

 more correct in anatomical description. I have therefore elsewhere 

 adopted for it the term of Mastihranchia^ (branchial lash). 



The same author has also proposed the classification of the macrura 

 according to their branchial arrangement. But the study of a larger 

 number of species is yet necessary, before we can see the advantage of 

 placing in separate families, animals that in form and structure generally 

 resemble each other, while others that are outwardly dissimilar are placed 

 in the same genus. 



During the voyage of the Challenger the lamented naturalist, Dr. 



• Meio-Tis, lash ; fipdyxtov, gill. 



