576 PROCEEDINOS OF THE NATIONAL MUSEUM. vol.47. 



fusion, SO that the long axis is actually transverse and not longi- 

 tudinal. 



In Naobranchia the sexual process is as long as the maxillipeds and 

 suggests very strongly the trunk of Lernaeo'podina; there is also a 

 carapace which covers the entire body. 



5. Finally in the genus Clavella there has been an even greater flex- 

 ion and fusion of the body, for now the sexual process is closer to the 

 second maxillae and sometimes is carried forward to a point between 

 them, so as to be concealed in side view. 



The transverse diameter is still longer than the longitudinal one, 

 and there are no signs of any carapace. 



TJie eye. — None of the adults in any genus possess eyes ; the eye in 

 this whole family is extremely rudimentary, appears only for a short 

 time during the development stages, and then entirely disappears.^ 



Tlie appendages. — In the adults of both sexes there are six pairs of 

 appendages, namely, two pairs of antennae, one pair of mandibles, two 

 pairs of maxillae, and one pair of maxilUpeds. The reason for regard- 

 ing the penultimate pair as second maxillae is that they appear in 

 early development in front of the suture which separates the head 

 from the thorax, while the posterior pair appear behind that sutiu-e.^ 



In the adult males of the genus Aclitheres there may be also one 

 or two pairs of very rudimentary swimming legs. But these are only 

 vestiges of the developmental stages and probably disappear at the 

 fii'st molt after the male has attached himself to the female. Kurz 

 claims (1877, p. 400) to have found in the female of Clavellisa emar- 

 ginata on the posterior end of the trunk the rudiments of the last pair 

 of swimming legs. Before admitting this claim we must consider 

 first the fact that only two pairs of legs appear dming development 

 and these are attached to the two anterior segments of the free thorax. 

 If either of these pairs remained in the adult stage they must have 

 migrated the whole length of the trunk in order to appear on its pos- 

 terior margin. On the other hand, it would be rather strange for the 

 rudiments of the fifth or sixth pair of legs to appear in the adult 

 when only two pairs appeared in the developmental stages. 



Again, if Kurz's three figures (pi. 25, figs. 8, 9, and 10) be carefuUy 

 compared with respect to the orientation of the trunk, it will be seen 

 that figure 8 (designated "Bauchansicht") actually represents the 

 ventral surface of the trunk and the dorsal surface of the cephalo- 

 thorax, except the head, which is turned in profile. In figure 10 

 (designated ''vom Bauch gesehen") the cephalothorax has been 

 turned forward out of its natural position, and we are actually looking 

 at the dorsal surface of both cephalothorax and trunk. But this is 



1 Proc. U. S. Nat. Mus., vol. 39, p. 204. Compare also fig. 13, p. 593. 



s Compare also Hansen, 1893, p. 421; Oiesbrecht, 1893, p. 84; Claus, 1895, p. 50; Wilson, 1910, p. 200; 

 1911, pp. 281 and 323. 



