| OCR Text |
Show 1903.] IN TIIE ‘ CHALLENGER ' COLLECTION. 73 The eye-stalks, the maxillipeds, and the four posterior pairs of the trunk-legs have been broken off. I am convinced that at least most, and perhaps all, these appendages possess some organs, and the lowest number the species possesses must therefore be about 150 ! On the distribution and direction of these organs the following remarks may be offered. The four organs on each side of the scutum are arranged rather close in a longitudinal row situated on the ridge bordering the branchial cavity above (fig. 2 a). The organ on the clypeus is large: one organ is situated on the segment bearing the antennulse, and one on the lower surface of the head near the lateral margin a little in front of the mandible ; these four organs look essentially downwards. The arrangement of the organs on the three posterior thoracic segments can be seen in figs. 2 i and 2 d. It is observed that two large organs are placed at the lower margin of hr. above trl.3 and of hr.l above trl.4 These organs look outwards and downwards, ard the part containing the glandular mass &c. behind the lens is somewhat protruding, wdiich produces an aspect as if these organs had been inserted on the end of a kind of rather thick, short stalk. The remaining organs on the segments mentioned are found on the lower surface (fig. 2 i) ; those placed at the inner angle of the legs are small or very small, while some in the median line are large. In fig. 2 i fifteen thoracic organs have been drawn ; the remaining eleven thoracic organs are situated on the anterior segments and arranged in a rather similar way. The four organs on the lower surface of each squama of the antenna are arranged for some distance in a row ; two of them are seen through the squama in fig. 2 c. The mandible (fig. 2 e) has one organ below at the antero-inferior margin near the insertion of the palp; another organ is seen on the lower surface of the first joint of the palp near its distal end. The first maxilliped (fig. 2 f ) has on the upper side one organ just at the origin of the exopod, and one on the lower side of the following joint of the endopod; the first-named organ looks forwards and a little inwards (fig. 2 g), and the upper margin above it is produced nearly as a lamella, overlapping the major part of the lens when seen from above (figs. 2 g & 2 n). Of the organs on the outer-in the natural position of the appendage in reality the lower-surface of mxp.2 (fig. 2 h), that at the base of the third joint is very small and the others large; the organ on the first joint looks essentially downwards, and is " stalked," as the above-described organs near the lower margin of the posterior branchiae. Of the three organs on trl.1, two are placed on the inner side of the long fourth joint, one near the base and the other near the distal end; the third organ is situated on the anterior side near its end. Each of the five anterior abdominal segments has a large organ on the lower part of the anterior margin of the lateral plate (figs. 2 d & 2 i) ; it looks forwards and somewhat downwards, besides sometimes a little outwards. Each of the two anterior segments has besides |
