^28 DR- J- D. F. GILCHRIST ON A FREE-SWIMMING 



at the tips of the antenmiles (sometimes absent), at the imier side o£ their 

 bases, on the lower lips (well marked), at the bases of the third maxilhped, 

 the first, second, and third walking-legs, and at the joints and tips of the 

 walking-legs with the exception of their exopodites which are unpigmented. 



The paired eyes are well developed, and are situated near the anterior 

 maro-in of the cephahc shield, to which they are attached by short stout 

 stalks. There is a median eye-spot. 



The aniennules project forward between the eyes. They show no traces 

 of segmentation, and the spines, which appear in the next stage, are still 

 covered by cuticle, though a few short terminal ones and a minute one at 

 a little distance from the free extremity can be made out. The bases of the 

 antennules are visible from the ventral side, and are situated slightly posterior 

 to the bases of the eye-stalks. In length the antennules are about three- 

 fourths of the length of the aiitennse. 



The antenna} are the most conspicuous organs, and are in length about 

 four-fifths of the breadth of the cephalic region. Each consists of a rather 

 long and stout protopodite, the main axis of which is continued into a 

 shorter, but also stout, exopodite, while the smaller endopodite appears as 

 a branch to this main stem, though a little later on (at the third moult) it 

 already exceeds the exopodite in length, and, ultimately, alone survives as the 

 main portion of the antenna. Near the base of the protopodite is a papilla- 

 like projection, apparently a masticatory process. From the posterior border 

 of the exopodite arises a series of long cuticular projections, each resting on 

 a ledge-like indentation of the exopodite. They form broad flat swimming- 

 blades, nearly touching each other at their origin, and beut dorsally at their 

 tips. They are provided with a single series of fine setse on each side. 

 There are five of them arising from the posterior margin of the exopodite and, 

 two from its extremity. In length the inner is a little over three times the 

 length of the exopodite, the terminal one being very much smaller. Into 

 this last and the one next it project two spines which become free at the next 

 stage. The endopodite is also provided with long flat cuticular processes, 

 similar to those of the exopodite, but only two in number. The first, or 

 inner, is shorter than the second. They arise from a common base, and 

 into each projects a spine from the tip of the endopodite. 



The upper lip is well developed and shows active movement in the living 

 state. 



The mandibles are sliort stout organs, with a broad base, and term.inate in 

 a short thick spine with about three denticulations. No trace of segmenta- 

 tion nor a biramose condition was seen. Their inner extremities are over- 

 lapped by the upper lip. 



The loiuer lip consists of two well-marked leaf-like lobes, which also 

 overlap the tips of the mandibles from below, and even the margin of the 

 upper lip to a slight extent. 



