PLANKTONETTA ATLANTICA. 135 



the pores being placed at about the most prominent part of 

 the curve. 



From the edge of the lip spring the arms. These are eight 

 in number ; six of them are arranged as a right, a left, and 

 an anterior pair, all of which radiate from the lip nearly at 

 right angles to the longitudinal axis ; there is also an upright 

 pair, taking origin right and left of the anterior pair, Avhich 

 lie at first nearly parallel to the long axis. The general 

 direction of the arms varies in different specimens, apparently 

 according to the amount of bad usage received in the tow-net ; 

 but the right and left pairs mostly bend aborally and pos- 

 teriorly, the anterior pair aborally and outward, the upright 

 pair anteriorly. The arms vary considerably in length, the 

 right and left pairs being the longest, the upright and anterior 

 pairs generally subequal. They are tubular, the cavity being 

 subdivided by laminre (fig. 7), and exhibit, except at the tip, 

 two layers, — an outer,'less refractile, which is continuous with 

 the spines, and an inner, more refractile layer, of which the 

 laminas form a part. The distribution of the spines is very 

 irregular, but near the plueodium they seem to be in pairs, 

 more or less opposite to one another, each pair in a plane at 

 right angles to its immediate neighbours. Distally the 

 arrangement is more irregular, and the spines closer together. 

 Dr. Borgert's specimens appear to have been somewhat more 

 variable than mine ; I therefore translate his description.^ 

 " At the distal end the arms run out into two to four diverg- 

 ing branches. These terminal branches are simple or forked, 

 in other cases with three, four, or even more tines ; in this 

 respect not only do the arms of the same specimen often show 

 variations, but even the terminal branches of one and the 

 same arm may be dissimilarly constructed. The surface of 

 the arms is beset with racemose lateral spines ; these carry on 

 their numerous long thread-like branches a terminal circlet 

 of four, more rarely five, short, thick, backwardly directed 

 hooks ; a little beyond these the thread carries another whorl 

 of three to five (generally four) somewhat larger and thinner 

 ^ ' Nordisclies Plankton,' op. cit. supra. 



