276 DISCOVERY Rf:PORTS 



Fourth limb. Endopod nearly as long as that of third and strongly kneed. 



Fifth limb. Varies from having an endopod of three segments to having one of five 

 which is feebly kneed but considerably shorter than that of the fourth. 



Sixth limb. Rarely not segmented and non-setose, most frequently not segmented 

 but setose, often with endopod having three to five segments indicated. 



There are always seven pairs of gills, the second to the eighth ; the first pair may or 

 may not be present as small buds. The following appears to be the most usual stage of 

 development : the second to sixth and the eighth gills of buds of one small branch, the 

 seventh of buds with two small branches arising from them. A variety of higher stages 

 of development occurred which showed that the order in which the gills branch is not 

 the same in all individuals. The highest development seen was the second to fifth gills 

 of two, the sixth to eighth of three, strong branches. 



The tergal collar of the first abdominal somite is the same as in the previous stage. 



Fur cilia, stage VI 



Description of more general characters based on the examination of sixty-four specimens, of the 

 mandibular palp on twenty specimens, of the limbs and gills on fourteen. Seventy specimens were 

 measured and were 6-2-9-3 mm. long. 



In this stage there is one terminal spine on the telson. 



The carapace may have as strong and distinctive a dorsal organ as in earlier stages, or 

 a smaller dorsal organ or only a crest ; even if it is only a crest it is higher and more 

 definite in form than anything which occurs in this stage of E.frigida. The frontal plate 

 is a triangle with straight margins or a lower triangle in which the lateral margins are 

 distally slightly concave. 



The antennular spine is nearly as long as, or much shorter than, the second pe- 

 duncular segment. The mandibular palp may be unsegmented but is usually segmented. 

 The degree of development of the thoracic limbs is as follows : 

 First limb. Either short with no gill bud, the endopod feebly kneed, or longer with a 

 very small or small gill bud and the endopod strongly kneed. 

 Second to fifth limbs. Endopods long and kneed. 



Sixth limb. Endopod of two to five segments and not kneed, or of five segments and 

 kneed. 



The first pair of gills may or may not be present as small buds. The second to fifth 

 may each consist of two unequal branches, the sixth of two, and the seventh and eighth 

 of three, roughly equal branches ; or the second to fifth may consist of two nearly equal 

 branches, the sixth to eighth of three unequal branches ; or the second to fifth may con- 

 sist of two equal and one much smaller branch, the sixth of three, the seventh of four, 

 the eighth of five, unequal branches. 



The tergal collar of the first abdominal somite is most frequently similar to that of the 

 two previous stages; it is sometimes absent, so that no connection between the tergal 

 wings can be seen. 



