12G NOTES ON THE COPErODA OF THE 



of feet, the left longer tliau the right, of three segments, with three 

 apical bristles, of which the middle is the longest, and a long outer 

 marginal bristle on the second segment; right foot smaller, indistinctly 

 three-segmented, with only two apical bristles of similar length. (PI. IX., 

 figs. 39, 40.) 



The genital segment is not so long as the next two; the furca is 

 longer than the anal, nearly four times as long as broad, and asym- 

 metrical, that of the right side shorter than the left. This Copepod 

 was frequently found in company with undoubted ^ examples of 

 Met. Normani. 



DicJiotomons hrancMng of tail seice. A curious condition was first 

 observed by me in many instances amongst the Copepoda (referred to 

 me by my friend Mr. Stanley Gardiner) from the ]\Ialdive Islands of 

 tlie Indian Ocean. This consisted of a branching and sub-branching 

 of the setcE of the tail, an attempt at dichotomous division, so that in 

 many instances the whole of the tail setae were converted into a sort of 

 brush. I had never observed this in any Copepoda from our more 

 northern regions, and looked upon it as a condition probably peculiar 

 to the Copepoda of the Maldive region ; but I have lately observed 

 exactly the same in two examples from the Atlantic taken west of 

 Valentia, in Ireland, viz. once in UndeucJiceta major and once in Euchceta 

 norvegica. In the Maldive seas it has occurred with great frequency in 

 Calamis vulgaris, and also in Galocalanus, Paracalanus aculeatus, Scolc- 

 cithrix Danae, UuchireUa hella. It will be observed that it is always in 

 the Amphaskandria that this condition occurs. In the Maldive Collec- 

 tion it is of such frequent occurrence that it suggests a special variety 

 in each instance. What the precise significance may be I do not know, 

 possibly a device to assist flotation, but it is curious that it should occur 

 also in examples from the North Atlantic. The dichotomous branching 

 is very irregular, sometimes of one seta only, or two, or all the setae of 

 one side only, or of both sides. 



PiEMARKS ON THE HORIZONTAL DISTRIBUTION OF THE COPEPODA. 



Calamis finmarchicus. Sars (Crustacea of Norway) has recently 

 endeavoured to distinguish the Northern and Polar form under the 

 name of C. flnmarchicus from a southern form C. helgolandicus, basing 

 his opinion upon the size, length of the antennae, shape of the head, and 

 structure of the fifth feet. I have very carefully compared examples 

 from Thorshaven, the cold area of the Faroe Channel, the warm area of 

 the Atlantic, and the English Channel, and I am of opinion that the 

 factors upon which Sars bases this distinction are too inconstant to 

 admit such a separation into specific forms. Examples from the 



