NOTES AND MEMORANDA. 153 



peduncle with membranous and flexible walls which soon bifurcate to 

 form other branches ; these are resolved into a number of elongated 

 filaments nearly alike, but without regularity, and having the appear- 

 ance of a spindle with delicate walls. 



If some coloured liquid is injected into the sinus at the base of 

 the branchial feet, the whole of this system may be easily filled and 

 the liquid followed not only in the branchial tuft, but also in an 

 irregular network sunk in the thick part of one of the leaflets of the 

 false abdominal feet and comparable to the entire branchial apparatus 

 of the ordinary Isopods. A marginal vessel serves to collect the blood 

 and to send it into the branchio-cardiac trunk. 



In all the other Isopods the false abdominal feet are very simple, 

 and wherever they are complex to meet the requirements of a more 

 active circulation, it is by the rudimentary foldings of the posterior 

 plate of these members. 



In lone and Kepon * branched appendages are found on the sides 

 of the body, but there are fundamental differences between these and 

 Bathynomus, not only in the position of the plumes, but in their 

 structure also. 



Though inhabiting great depths, the eyes are well developed, each 

 having about 4000 facets, and in place of being at the toj) of the head 

 they occupy its inferior face, and are placed beneath the frontal 

 margin on each side of the base of the antennae. 



Bathynomus is separated by important characters from all other 

 Isopods, and justifies its being placed in a new family of " brauch- 

 iferous Cymothoadians." 



Limicolous Cladocera. — In the introductory part of a paper on 

 these Entomostraca,! Dr. W. Kurz gives an account of the main 

 difference between these mud-dwellers and their free-swimming 

 congeners. The distinctive characters of the former are due, firstly, 

 to the increased pressure of water to which they are subjected ; 

 secondly, to the thickness of the mud in which they live ; and thirdly, 

 to the altered relation of the gases absorbed in the water at a 

 considerable depth below the surface. The first two of these con- 

 ditions give rise to the thick integument and clumsy form which 

 characterize the limicolous species. The carapace is strengthened 

 either by the thickening of its cuticle or by the remarkable circum- 

 stance that, at the moult, the old armour is not cast ofP, but remains 

 superposed on the newer and larger parts beneath, like an old-fashioned 

 " spencer " over a coat ; three or four carapaces of progressively 

 increasing size may thus be seen in a single individual. The 

 antennae of the limicolous forms are comparatively very short and 

 stout, and the setae on them are not feathered. The whole body has 

 a rounded form, and the brood-pouch is extended laterally, not 

 vertically as in the free forms. As a rule they swim with the 

 dorsal surface downwards. The power of swimming seems to be in 

 inverse ratio to the size of the post-abdomen and the complexity of 



* Spelt Kepon by A. Milne-Edwurds ; Kcponc by Adam White ; and Cepon by 

 Duvcrnoy. 



t 'Zeitsch. f. wibs. Zoologie,' vol. xxx. Suppl. (1878) p. 3[)2. 



