MAPPHYSA SANGUINEA. 445 



In its progress backward the foot undergoes considerable change, the dorsal cirrus 

 increasing in bulk whilst the superior lobe increases in depth and thickness and develops 

 a posterior flap which is prominent superiorly. At the tenth foot, for example (Plate 

 LXXIV, fig. 8 a), a posterior view shows ja broadly conical superior lobe, the posterior 

 flap projecting superiorly and sloping inward inferiorly, the tuft of simple dorsal bristles 

 slanting upward and outward above the spines, whilst the inferior jointed bristles project 

 below it. The ventral lobe is conical with a long line (margin) inferiorly, corresponding 

 to the bulbous border. 



About the twenty-first foot, sometimes a little in front, a clavate process appears at 

 the inner base of the dorsal cirrus, the first indication of the branchias, which thus 

 pertain to the dorsal cirrus. In an example in which these organs began on the twenty- 

 first foot, the twenty-second had a simple but longer process. On the twenty-third the 

 increasing process had a short spur on its inner side. Both processes had considerably 

 increased in length on the twenty-fourth foot. The twenty-fifth and twenty-sixth had 

 each two divisions springing from a common base, and so had the twenty- seventh on the 

 left, but the right branchia of the twenty-seventh had a stem with three divisions (Plate 

 LXXIV, fig. 8). Four divisions characterized the thirty-second foot, and the processes 

 were longer. Five divisions soon make their appearance, and about the fiftieth foot there 

 are six (in the large example taken as the type), and these form a pectinate series which 

 project upward from a more or less horizontal stem, the longest being to the exterior, the 

 shortest to the interior. This condition, however, may arise from the last formed process 

 budding from the base of that adjoining, and becoming continuous with the oblique stem. 

 The basal trunk from which all these arise is stout. 



Behind the foregoing the maximum number of branches is found, viz. eight, and as 

 the processes are long and bright red, they form a conspicuous series along the dorsum. 

 After attaining the maximum the branchiae gradually diminish in number, and by-and-by 

 in size, until in front of the tail a short process of two divisions and then of one occurs, 

 the last twelve to fifteen segments or thereabout being devoid of them. Probably the 

 condition as regards reproduction of the tail has much to do with the arrangement in 

 individual specimens. In sickly and dying forms the branchiae become pale. 



An urn-shaped Infusorian (somewhat like Biosceca) occurred in great numbers on the 

 branchiae. 



The dorsal bristles, which leave the foot above the spines, have anteriorly translucent 

 slender straight shafts, the terminal region being marked from these by a slight 

 curve, beyond which the tip appears to be flattened, is a little dilated, and then tapers to a 

 fine point. In the middle of the body the curve alluded to is more gentle (Plate 

 LXXXIII, figs. 5 and 5 a, and also Plate LXXVII, fig. 16), and the dilatation of the tip more 

 distinct. The edge is also very finely serrated. Amongst the foregoing is a group of 

 brush-shaped bristles (Plate LXXXIII, fig. 5 a), the distal margin being of considerable 

 breadth and with a series of fine teeth, the edge at each side having a longer process. 

 A few of these appear on the tenth foot and continue to the posterior end, where (just in 

 front of the tail) they increase in size and some have considerably coarser fimbriae (Plate 

 LXXXIII, fig. 5 b) which are also oblique. 



In the inferior group of bristles the shaft is curved toward the tip, dilated and 



