FACKAKD.] MORPHOLOGY OF PHYLYOPODA. 393 



Except tLe diminished size of tlie gill, the only other important modi- 

 fication in the foot is the large triangular sixth endite, which shares in 

 jinvt the enlargement of the subapical lobe. 



In the BrancMpodidcej where the head, thorax, and abdomen are clearly 

 .differentiated, all the legs are thoracic, there being no abdominal ap- 

 pendages except the gonopodaand the cercopoda. The legs also differ 

 Eiuch more from the two lower Phyllopodous families than those of the 

 members of these two families from each other. The axial relations of 

 the Branchipod limb are much as in the Lininadiadcf;, the axis being not 

 only entirely without any traces of joints, but not differentiated in any 

 such waj' as in the Ajjodidce from the endites or exites ; in this respect 

 the limb corresponds to those of the Limnadiadcc. The chief difference, 

 however, from the two lower families is the absence of a functional 

 gnathobase. The basal or first endite, as seen in the figures on Plates 

 VIII-XIV, forms a very short and broad uniformly curved lobe with no 

 armature at the base, the edge being uniformly fringed with very long, 

 delicately setulose setae ; the lobe is weak and only adapted for swim- 

 ming. By reference to Plate XIV, fig. 4, it will be seen, as in the genus 

 Thamnocephalus, that the sternal groove along the under side of the body 

 is broad, that the endites on either side are quite remote from each other, 

 so as to be of little use in retaining the food or prey. This figure also 

 shows the relations of the endites to the leg or axis, and of the leg as a 

 whole to the body. The second endite is in general about one-third as 

 wide as the first, while the third and fourth are minute, more or less 

 pointed, and provided with three or four long setulose or ciliated setae. 



The great size and breadth of the fifth and sixth endites constitute a 

 characteristic and diagnostic feature of the family. The fifth is very 

 large and squarish or rounded, and armed on the edge with short re- 

 mote spines. The sixth is more or less paddle shaped, subtriangular, 

 and provided with a fringe of very long and rather stiff' seta3, being well 

 adapted for use in swimming; this lobe, with the fifth, is mainly con- 

 cerned in locomotion. The two exites, the fiabellum and gill, are in 

 this family much more alike than in the other two groups. The gill (br) 

 in Artemia, Branchinecta, Brancliipus is small, oval in outline, and much 

 as in the Apodidce, but in Chirocepliahis, and esi)ecia]ly in Streptocepha- 

 Jus, it becomes much larger, while in Thamnoceplialus it is much like the 

 fiabellum {hr') in size and form as well as in structure. 



It is interesting to observe, from the drawings of Claus and of Gissler, 

 that in the development of the legs in the early larval stages the endites 

 are the fij^st to be developed, the exites not appearing until some time 

 after the six inner lobes are indicated. 



The abdomen and the abdominal Ze</s'(Uropoda). — These are not present 

 in the Branchipodidce, and in the Limnadiadw and Apodidce they do not 



■whole of the abdomen not covered by the shield over the edge of the carapace of the 

 female to her ventral side. These motions were wholly similar to those made by the 

 male Brancliipus with its body during sexual congress, so that I have no doubt that the 

 smaller individual was the male, and that the whole performance was none other than 

 the fertilization of the gill-foot. The male repeated this act upon all the other 

 females present through a period of several days. Then a pause ensued, whereupon 

 the exhibition began anew. 



During the act of copulation the egg-sac of the $ came in contact with the 11th 

 feet of the ^ ; but the whole occurrence was so short, the animals going under and 

 turning themselves several times, that it was difficult to give a clear idea of the rela- 

 tion of the body parts to one another. 



Through a later anatomical examination of the male I found my view completely 

 coulirmed. It was filled abundantly with testes-tubes, finger-shaped, the branches 

 filled with seminal cells, as were described by Kozubow ski. He then quotes Kozu- 

 bowski's similar observations on the mode of copulation, from which Brauer's obser- 

 vations differ somewhat. 



