13° 



DISCOVERY REPORTS 



nerve, neither was it observed in the specimen of D. australis from St. 149 represented 

 in Fig. 73 A ; but a very slender nerve strand was present in one of the specimens 

 from St. 154. 



As anticipated, the ventral nerve chain in Decolopoda possesses six, instead of the 

 usual five, ganglionic masses. The lateral nerves to palp, ovigers and each leg soon 

 bifurcate. 



ABNORMALITIES 



Abnormalities occur very infrequently in Pycnogonida ; at any rate, in the large 

 Discovery collection the following few examples are all that were noted, ^ apart from 

 the occasional loss and subsequent regeneration of a walking leg. 



I. Palp. The tip of the palp is sometimes slightly abnormal, e.g. (i), the right palp 

 oi Colossendeis tortipalpis, n.sp.,rcpvtsentedm Fig.2e;(ii),the left palp oi A7nmothea,sp.} 

 described on p. 108 and (iii), the right palp of the holotype of Ammothea calmani, n.sp. 

 (Fig. 74 a), where segments 7 and 8 appear to be fused. In the last example the notch 

 X (Fig. 74 a) may represent the beginning of bifurcation or of segmentation. 



Fig. 74. a. Ammothea calmani, n.sp. Holotype. Segments 4-9 of right 

 palp — segments 7 and 8 are apparently fused 1x15 and 20. 



b. Decolopoda antarctica, Bouvier. Proximal portion of abdomen, 

 showing additional small clavate process on right side: x 20. 



c. IPallenopsis sp. St. 256. Terminal segments of oviger showing 

 distinct bifurcation: xioo. 



The most extreme case of abnormality is the tripartite palp of Nymphon proceroides, 

 Bouvier (Fig. 75). Here a is probably the original left palp, bearing the two extra palps 

 on the outer distal angle of the second segment. The long axes of palps a, b and c lie 

 in one plane ; ^ is a mirror image of a and c of b, according to the two rules enunciated 

 by Bateson (1894, p. 479). 



1 Two of the abnormalities figured (Figs. 74 a, 75) occurred in specimens from other collections. 



