PRAWNS FROM LAKK TANGANYIKA. 



437 



appears more tlistiuctly <lefiiie<l and exliibits a well-marked 

 trituratiMg surface. 



'l^lie maxillce (tigs. 6 & 7) scarcely differ from tlioss in the pre- 

 ceding stage, except in a somewhat richer supply of marginal 

 spines and seta3. 



Tiie maxilUpeds {&gs. 8-10), on the otlier hand, have been con- 

 spicuously transformed, and now look very dissimilar. In the 

 1st pair (fig. 8) only a slight rudiment of the end(>i)odite is left, 

 and the exopodite also is considerably reduced and apparently 

 quite immobile, without any setie at the tip, and having the distal 

 part curved downwards, (in the 2nd pair of maxillii)eds (fig. 9) 

 the endopodite has assumed the characteristic securiform shape 

 observed in the adult animal, the outer two joints forming to- 

 <rether a broad plate folded upon the proximal pait and armed at 

 the inner edire with a number of spiniform anteriorly curving 

 seta?. On tlie ;5rd pair of maxillipeds (fig. 10) finally the endo- 

 podite has preserved its pediform shape, but is considerably 

 prolonged, forming a nearly straight cylindric stem almost twice 

 as long as the exopodite. The latter, as in the preceding pair, is 

 extended straight anteriorly, and appears to be very little mobile. 



The chdipeds (fig. 11) have increased in length, and now 

 exhibit the full number of joints. On the hand, one of the 

 finders (dactyl us) has been well defined at the base, and connected 

 witb the hand by a very mobile articidation ; on the tip of each 

 fino-er a short claw-like spine has developed in addition to the 

 bristles, the number of which is considerably increased. The 

 seta; on the other joints are, howevei-, shorter and less numerous 

 than in the preceding stage. Outside the basal part a very small 

 and ii-regular protuberance is seen, indicating the place where tho 

 exopodite has originally been attached. 



The ^^ere/opofZ« (tigs. 12 & 13) are somewhat longer than the 

 chelipeds and (juite normal in sti'ucture. The dactylar joint 

 nearly agrees both in shape and armature with that in the adult 

 animal, as described by Dr. Caiman. Outside the basal jointof 

 the two anterior pairs (fig. 12) a minute protuberance quite 

 similar to that occurring in the chelipeds is seen, indicating the 

 original presence of exopodites on these legs. In the last pair 

 (fig° 13) no trace of such a protuberance is to be detected. 



Above the bases of the legs, except the last pair, and covered 

 by the lateral parts of the'carapace, the gills have developed, 

 forming on each side a regular series, as indicated in fig. 2. 



The pleopoda (tig. 14) are now freely mobile and have the 

 terminal lamelUe fringed with long ciliated seta?. The number 

 of these seta) is, however, as yet very limited, only eight being 

 counted on the outer lamella and six on the inner. All these 

 seta? exhibit close to the base a very conspicuous joint. 



The telso/i (i^g. 15) does not differ much in shape from that 

 in the preceding stage; but the number of apical spines has 

 diminished, only five such spines being present. On the other 

 hand, three pairs of lateral denticles have appealed, the outer- 



