50 



that I observed them also on the crest of the hibrum in one of the specimens of /. Cuiiiingi 

 from Station 86 (PI. IV, fig! 22). 



The palpi of the labrum are small, rounded at their ends; the hairs on the palpi 

 form a not very dense tuft at the extremity, those on the palpi of both sides hardly touching 

 one another when in the natural position. The outer margin bears a row of e.xtremely 

 minute hairs. 



Mandibles. In one of the .specimens from Station 47 the upper edge of the second 

 tooth was not pectinated. The inferior angle is only slightly produced in all the mandibles I 

 investigated; it is pectinated as figured (fig. 22a). 



Maxillae (PI. V, fig. i). Edge very indistinctly indented; it supports, besides the three 

 upper large spines, a number of moderately strong spines, which can hardly be divided into 

 stronger and more delicate ones. Maxillae small, apodeme short. 



The shape of the outer maxillae (fig. 2), of the conical prominence clothed with 

 bristles and coloured purple lying over the infra-oesophageal ganglion between the bases of the 

 first pair of cirri, corresponds exactly with Darwin's description of the same parts in /. Cmiiingi. 



Cirri. The first cirrus has the rami unequal in length by from 2 to 5 segments, by 

 about two segments in /. Citiiriiigi, according to Darwin. I dissected in all six specimens of 

 /. siliogac and I found the following numbers of segments for the first cirrus: 21 — 17, 2c — 16, 

 17 — 14, 17 — 13, 17 — 12 and 14 — 12. These numbers show greater variety than is the case 

 in most other Lepadids. 



(In a specimen of /. Ciimingi I found a difference of 5 segments in the first pair of 

 cirri, in another of 3 segments). 



The other cirri conform in general to Darwin's description of /. Cniiiingi. Investigating 

 carefully the arrangement of the bristles on the segments of the sixth cirrus, I found very often 

 on the anterior surface not three pairs of spines, the lowest pair being minute, but four pairs, 

 three of which were stronger, the fourth very delicate. A number of segments showed this 

 arrangement, others on the same cirrus the three pairs as described by Darwin for /. Ciiinmgi. 

 (On the 6"^ cirrus of a specimen of /. Cumingi collected at Station 86 I also found four pairs of 

 bristles on some of the seg^ments — however, the number of seornents showinof this arrangement 

 was very small). 



The caudal appendages have from 1 7 to 13 segments. The upper segments which 

 in /. Cumingi "are slightly constricted round the middle, so that they resemble in a small 

 degree an hour-glass" (Darwin), in /. sibogae do not show the hour-glass shape as a rule. In 

 some specimens the two last joints show a trace of that peculiar shape, which I found distinctly 

 developed in the last six segments of the caudal appendages of specimens of /. Cumingi. As 

 in this species the caudal appendages of /. sibogae are as long as or slightly longer than the 

 pedicels of the sixth cirrus. 



The egg-lamellae are not very large, nor is the number of eggs in each lamella: a 

 lamella contains one layer of eggs only, in that of a medium-sized specimen from Station 61 

 I counted about 240 eggs. In each lamella the eggs are kept together by an extremely delicate 

 and clear membrane, which surrounds eaeh &^'g as a capsule. At one place the margin of 



5° 



