430 TROF. G. O. SARS ON 



scarcely longer than the basal part and divided only into three 

 joints. In the other two pairs (figs. 10, 11) the middle joint 

 appears faintly subdivided behind the middle. Very small setas in 

 process of formation are seen on the terminal joint, and partly 

 also on some of the other joints inside. The exopodite, which is 

 movably attached to the outer distal corner of the basal pai-t, is 

 in all three pairs of exactly the same ajopearance, forming a very 

 flexible, soxnewhat flattened stem with four long ciliated setfe at 

 the end, two of them issuing from a minute apical joint. In the 

 two posterior pairs another rather small seta is seen issuing inside 

 at some distance from the end. 



Occurrence. — Several specimens of this peculiar larva, all closely 

 agreeing both in size and structure, were obtained from four 

 different samples. Two of these samples were taken at Niamkolo 

 (S. end of lake), another at Mbete (likewise at the south end of 

 the lake), and the fourth at Sumbu (S.W. of lake). 



ZoEA No. 2. (PI. LYIII.) 



The differences between this and the preceding larva are so 

 conspicuous, that I think we are justified in assimiing that 

 it belongs to a different kind of prawn. It is of much larger 

 size, and in some respects exhibits considerably more advanced 

 development. Yet the imperfect sti-ucture of the oral parts, in 

 connection with some other features, would seem to prove that 

 it in reality represents a very early larval stage. 



The length of the specimen examined is about 1'60 mm., and 

 the size of this larva is accordingly more than twice that of the 

 preceding one, and nearly equals that indicated by Prof. Daday 

 for tlie earliest observed stage (Euzoea) of Caridina nilotica. The 

 present larva cannot, however, by any means belong to that 

 species, which does not occur in Lake Tanganyika, but must 

 be derived from some other form of prawn, in which the ova 

 are of a similar size to those in the said species. Consulting 

 again the paper of Dr. Caiman, we find that in this respect only 

 one of the Tanganyika prawns would seem to come under con- 

 sideration, viz., Caridella cunningtoni Caiman, the ova of which 

 are in reality much larger than in any of the other forms 

 examined. I am therefore led to the conclusion that the present 

 larva in all probability may be an early stage of that form. 



As compared with the preceding larva, the body (PI. LVIIT. 

 figs. 1 & 2) appears rather short and stout, with the anterior divi- 

 sion considerably dilated and the posterior one less slender. 



The carapace is somewhat gibbously vaulted in its anterior 

 part, and, as in the preceding larva, is slightly emarginated 

 behind in the middle. At the antero -lateral corners a well-mai'ked 

 spine occurs; but this spine does not project laterally (fig. 1). 

 Anteriorly the carapace is produced into a well defined, though 

 quite simple narrow spiniform rostrum, which projects distinctly 

 in front. 



